Photothermographic imaging material

ABSTRACT

A photothermographic imaging material having high sensitivity and superior temporal storage stability. The photothermographic imaging material includes silver halide on at least one side of a support, and includes at least one kind of the compounds represented by the following general formula (1).

BACKGROUND OF THE INVENTION

[0001] 1. Field of the Invention

[0002] The present invention relates to a photothermographic imagingmaterial.

[0003] 2. Description of the Related Art

[0004] In Recent years, in the field of medical services, reduction ofprocessed waste fluids has been intensively desired in view ofenvironmental protection and space saving. In this concern, a technologyin respect of photosensitive thermal development photograph materialsused for medical diagnoses and photographic techniques, which can beexposed efficiently by a laser image setter or a laser imager and canform black images provided with high resolutions and definition, hasbeen required. With such photosensitive thermal development photographmaterials, it becomes needless to use solution-type processingchemicals, and it enables the users to be implemented with a thermaldevelopment process system that is simpler and does not destroy thenatural environment.

[0005] On the other hand, the semiconductor laser technology having beenprogressing in recent years has allowed image output apparatuses formedical use to be compact in their sizes. Naturally, a technology inrespect of infrared-sensitive thermal development photograph materialscapable of utilizing semiconductor laser as a light source has beendeveloped also, and various spectro-sensitization technologies have beendisclosed (see JP Hei-3-10391B, JP Hei-6-52387B, JPTokukaihei-5-341432A, JP Tokukaihei-6-194781A, JP Tokukaihei-6-301141A).

[0006] However, in the photothermographic imaging materials with whichrecordings are achieved by using a laser light source, it is desiredthat the material can greatly absorb light in accordance with abright-line wave length. However, colorants each having its maximumabsorption band in a region of red to near infrared have long conjugatechains and are inclined to receive influences by the environment. As aresult, though the colorant has a high molar absorption coefficient in asolution, there happens easily such a phenomenon that the colorantdisappears during the preparation, or that the colorant takes a numberof conformations and forms a wide absorption spectrum with small maximumabsorption intensity in a photosensitive material. Further, the intervalbetween the lowest vacant level and the highest occupied level isnarrow, and the lowest vacant level and the highest occupied level areapproximate to the conduction band of silver halide particles.Therefore, there happens such a problem that fogging can be causedeasily, or that the sensitivity can be lowered.

[0007] Hence, it has been desired to provide an infrared-sensitivephotothermographic imaging material having a photosensitive spectrumthat intensively absorbs light in a region of red to near infrared andan infrared-sensitive photothermographic imaging material that is highlyphotosensitive, causing less fogging and less deterioration in theperformance even after a substantial time elapse.

[0008] In order to resolve the aforementioned problems, varioustechniques in connection with infrared sensitizing colorants and thosefor combining infrared sensitizing colorants have been disclosed (seeU.S. Pat. No. 3,582,344, U.S. Pat. No. 4,975,362, U.S. Pat. No.5,013,642, EP 821811, JP Tokukaihei-9-510022A, JP Tokukaihei-5-72659A,JP Tokukaihei-9-292673A, JP Tokukaihei-9-166844A, JPTokukaihei-9-281631A, JP Tokukaihei-9-281639A, JP Tokukaihei-9-288327A,JP Tokukaihei-10-73900A, JP Tokukaihei-10-123663A, JPTokukaihei-10-123665A).

[0009] However, it has been noted that the photosensitivity is notsufficient with such infrared sensitizing colorants as disclosed inthose references, and that there is a problem of less photosensitivityand increasing fogging at the time of development and during thepreservation lasting for a substantial time elapse. Hence, it has beendesired to be improved.

SUMMARY OF THE INVENTION

[0010] The present invention was aimed at implementing theabove-described requirements, and it is an object of the presentinvention to provide a photothermographic imaging material with highphotosensitivity and excellent shelf life lasting for a substantial timeelapse. More particularly, the object of the present invention is toprovide a photothermographic imaging material that has high sensitivitybut causes less fogging against the exposure to infrared laser beams andless deterioration in the properties during the preservation periodlasting for a substantial time elapse.

[0011] According to the first aspect of the present invention, aphotothermographic imaging material comprises photosensitive silverhalide on at least one side of a support, and at least one of compoundsrepresented by the following general formula (1).

[0012] Wherein the L₁₁ to the L₁₇ represent each independently ahydrogen atom, a halogen atom, an amino group, an alkylthio group, anarylthio group, a lower alkyl group, a lower alkoxy group, an aryloxygroup, an aryl group or a heterocyclic group, or a non-metal atom grouprequired for bonding the L₁₁ and the L₁₂, the L₁₂ and the L₁₃, the L₁₃and the L₁₄, the L₁₅ and the L₁₆, and the L₁₆ and the L₁₇, respectively,to form 5- to 7-membered rings; the R₁ and the R₂ represent eachindependently an aliphatic group; the R₁ and the L₁₁, and the R₂ and theL₁₄ can be bonded each other to form a 5- to 7-membered cyclic structurerespectively; the Ar₁ and the Ar₂ represent each independently an arylgroup or a heterocyclic group; the X₁₁ represents an ion required foroffsetting electric charges in a molecules; and n represents the numberof ions required for offsetting electric charges in the molecules.

[0013] The material according to the first aspect of the invention hashigh sensitivity and superior temporal storage stability, and further indetail, the material has high sensitivity and low fog for infrared laserexposure, and show small variety in the properties thereof according tothe temporal storage.

[0014] The material according to the first aspect preferably comprisesat least one of compounds represented by the following general formula(2).

[0015] Wherein the L₂₁ to the L₂₄ represent each independently ahydrogen atom, a halogen atom, an amino group, an alkylthio group, anarylthio group, a lower alkyl group, a lower alkoxyl group, an aryloxygroup, an aryl, a heterocyclic group, or a non-metal atom group requiredfor bonding the L₁₁ and the L₁₂, the L₁₂ and the L₁₃, the L₁₃ and theL₁₄, the L₁₅ and the L₁₆ and the L₁₆ and the L₁₇ can be bonded eachother respectively to form 5- to 7-membered rings; the R₃ and the R₄represent each independently an aliphatic group; the R₃ and the L₂₁, andthe R₄ and the L₂₄ can be bonded each other to form a 5- to 7-memberedcyclic structure, respectively; the X₂₁ represents an ion required foroffsetting electric charges in the molecules; the m represents thenumber of ions required for offsetting electric charges in themolecules; the R₂₁ to the R₂₄ represent each independently a hydrogenatom, an alkyl group or an aryl group; and the R₂₅ to the R₃₂ representa group capable of being substituted on a benzene ring; the R₂₅ and theR₂₆, the R₂₆ and the R₂₇, the R₂₇ and the R₂₈, the R₂₉ and the R₃₀, theR₃₀ and the R₃₁ and the R₃₁ and the R₃₂ can be bonded each otherrespectively to form cyclic structures; the R₂₇ is neither an aryl groupnor a heterocyclic group.

[0016] According to the material of first aspect, the compoundrepresented by the general formula (1) is preferably a compoundrepresented by the following general formula. (3).

[0017] Wherein the L₁₁ to the L₁₇ in the general formula (3) aresynonymous with the L₁₁ to the L₁₇ in the general formula (1); the R₁and the R₂ in the general formula (3) are synonymous with the R₁ and theR₂ in the general formula (1); the X₁₁ in the general formula (3) issynonymous with the X₁₁ in the general formula (1); the n in the generalformula (3) is synonymous with the n in the general formula (1); and theAr₃ and the Ar₄ represent each independently an aryl group.

[0018] According to the material of first aspect, the compoundrepresented by the general formula (1) is preferably a compoundrepresented by the following general formula (4).

[0019] Wherein the L₁₁ to the L₁₇ in the general formula (4) aresynonymous with the L₁₁ to the L₁₇ in the general formula (1); the R₁and the R₂ in the general formula (4) are synonymous with the R₁ and theR₂ in the general formula (1); the X₁₁ in the general formula (4) issynonymous with the X₁₁ in the general formula (1); the n in the generalformula (4) is synonymous with the n in the general formula (1).

[0020] According to the material of first aspect, the compoundrepresented by the general formula (1) is preferably a compoundrepresented by the following general formula (5).

[0021] Wherein the L₁l to the L₁₄ in the general formula (5) aresynonymous with the L₁₁ to the L₁₄ in the general formula (1); the R₁and the R₂ in the general formula (5) are synonymous with the R₁ and theR₂ in the general formula (1); the X₁₁ in the general formula (5) issynonymous with the X₁₁ in the general formula (1); the n in the generalformula (5) is synonymous with the n in the general formula (1); and theR₃₁ to the R₃₄ represent each independently a hydrogen atom, an alkylgroup or an aryl group.

[0022] According to the material of first aspect, the compoundrepresented by the general formula (2) is preferably a compoundrepresented by the following general formula (6).

[0023] Wherein the L₂₁ to the L₂₄ in the general formula (6) aresynonymous with the L₂₁ to the L₂₄ in the general formula (2); the R₃and the R₄ in the general formula (6) are synonymous with the R₃ and theR₄ in the general formula (2); the X₂₁ in the general formula (6) issynonymous with the X₂₁ in the general formula (2); and the m in thegeneral formula (6) is synonymous with the m in the general formula (2);the R₂₁ to the R₂₄ in the general formula (6) are synonymous with theR₂₁ to the R₂₄ in the general formula (2); and the R₄₁ and the R₄₂represent each independently an unsubstituted lower alkyl group, acycloalkyl group, an aralkyl group, an aryl group or a heterocyclicgroup.

[0024] The material according to the first aspect preferably comprises acompound represented by the following general formula (7).

[0025] Wherein the R₁₁ and the R₁₂ represent each independently hydrogenatom, 3- to 10-membered nonaromatic cyclic group or 5- or 6-memberdaromatic cyclic group; the R₁₃ and the R₁₄ represent each independentlyhydrogen atom, alkyl group; aryl group or a heterocyclic group, the Qrepresents a substituent on the benzene ring; n is 0 or an integer of 1or 2; and the Q are same or different from one another when the Q isplural.

[0026] According to the material of the first aspect, the photosensitivesilver halide is preferably chemically sensitized.

[0027] The material according to the first aspect comprises aphotosensitive emulsion comprising the photosensitive silver halide anda non-photosensitive aliphatic silver carboxylate;

[0028] wherein the photosensitive silver halide is not contained in asynthesis of the non-photosensitive aliphatic silver halide, and ismixed with the non-photosensitive aliphatic silver carboxylate after acompletion of the synthesis to prepare the photosensitive emulsion.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

[0029] Hereinbelow, the present invention is explained further indetail. The thermophotographic imaging material of the inventioncomprises photosensitive silver halide on at least one side of asupport, and at least one of compounds represented by the above generalformula (1).

[0030] In the general formula (1) as described above, L₁₁ to L₁₇represent each independently hydrogen, a halogen atom, amino, alkylthio,arylthio, lower alkyl, lower alkoxy, aryloxy, aryl or a heterocycle;where the halogen atom includes fluorine, chlorine, bromine and iodine;amino includes substituted and unsubstituted amines, such as amino,dimethylamino, diphenylamino and methylphenylamino; alkylthio includes,for example, methylthio, ethylthio and benzylthio; arylthio includessubstituted and unsubstituted arylthio groups, such as phenylthio andm-fluorophenylthio; the lower alkyl is a straight-chain or branchedalkyl having carbon atoms not more than 5, that is specifically methyl,ethyl, propyl, butyl, pentyl, isopropyl and the like; the lower alkoxyis an alkoxy containing carbon atoms not more than 4, that isspecifically methoxy, ethoxy, propoxy, isopropoxy and the like; aryloxyincludes substituted and unsubstituted aryloxy groups, that arespecifically phenoxy, p-tolyloxy, m-carboxyphenyloxy and the like; arylincludes substituted and unsubstituted aryl groups, for example, phenyl,2-naphthyl, 1-naphthyl, o-tolyl, o-methoxyphenyl, m-chlorophenyl,m-bromophenyl, p-tolyl and p-ethoxyphenyl; and the heterocycle includessubstituted and unsubstituted heterocycles, for example, 2-furyl,5-methyl-2-furyl, 2-thienyl, 2-imidazolyl, 2-methyl-1-imidazolyl,4-phenyl-2-thiazolyl, 5-hydroxy-2-benzothiazolyl, 2-pyridyl and1-pyrrolyl. These groups as recited above can have a substituent of anyof phenyl, halogen, alkoxy, hydroxy and the like. The substituents to besubstituted on the above-recited groups are preferably hydrogen, loweralkyl, a halogen atom or aryl, and more preferably lower alkyl or aryl.

[0031] L₁₁ and L₁₂, L₁₂ and L₁₃, L₁₃ and L₁₄, L₁₅ and L₁₆, and L₁₆ andL₁₇, can bond with each other respectively, to form 5- to 7-memberedrings, and L₁₁ to L₁₇ each represents a nonmetal atom required forforming a 5- to 7-membered ring. The 5- to 7-membered rings to be formedinclude, for example, a cyclopentene ring, a cyclohexene ring, acycloheptene ring and a decalin ring. In addition, any of these ringscan further have a substituent of lower alkyl, lower alkoxy and aryl,which are exemplified for L₁₁ to L₁₇ in the above. Among theaforementioned rings, it is preferable to form a cyclopentene ring or adecalin ring, and more preferably a decalin ring.

[0032] R₁ and R₂ represent each independently an aliphatic group. Thealiphatic group includes, for example, straight-chain or branched alkylseach containing 1 to 30 carbon atoms (including methyl, ethyl, propyl,butyl, pentyl, isopentyl, 2-ethylhexyl, octyl, decyl and the like),alkenyls each containing 3 to 30 carbon atoms (including 2-propenyl,3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl,4-hexenyl and the like), and aralkyls each containing 7 to 30 carbonatoms (including benzyl, phenetyl and the like). Among the groupsrecited above, preferred are straight-chain alkyls each containing 1 to20 carbon atoms or alkenyls each containing 3 to 20 carbon atoms.

[0033] The aliphatic groups exemplified above can further includesubstituents, and such substituents include, for example, a halogen atom(e.g., fluorine, chlorine, bromine, etc.), vinyl, aryl, (e.g., phenyl,p-tolyl, p-bromophenyl, etc.), trifluoromethyl, alkoxy (e.g., methoxy,ethoxy, methoxyethoxy, etc.), aryloxy (e.g., phenoxy, p-tolyloxy, etc.),cyano, sulfonyl (e.g., methanesulfonyl, trifluoromethanesulfonyl,p-toluenesulfonyl, etc.), alkoxycarbonyl (e.g., ethoxycarbonyl,butoxycarbonyl, etc.), amino (e.g., amino, biscarboxymethylamino, etc.),a heterocyclic group (e.g., tetrahydrofurfuryl, 2-pyrrolidinone-1-yl,etc.), acyl (e.g., acetyl, benzoyl, etc.), ureido (e.g., ureido,3-methylureido, 3-phenylureido, etc.), thioureido (e.g., thioureido,3-methylthioureido, etc.), alkylthio (e.g., methylthio, ethylthio,etc.), arylthio (e.g., phenylthio, etc.), heterocyclic thio (e.g.,2-thienylthio, 3-thienylthio, 2-imidazolylthio, etc.), carbonyloxy(e.g., acetyloxy, propanoyloxy, benzoyloxy, etc.), acylamino (e.g.,acetylamino, benzoylamino, etc.), thioamide (e.g., thioacetoamide,thiobenzoylamino, etc.), sulfo, carboxy, phosphono, sulfato, hydroxy,mercapto, sulfino, carbamoyl (e.g., carbamoyl, N-methylcarbamoyl,N,N-tetramethylenecarbamoyl, etc.), sulfamoyl (e.g., sulfamoyl,N,N-3-oxapentamethyleneaminosulfonyl, etc.), sulfonamide (e.g.,methanesulfonamide, butanesulfonamide, etc.), sulfonylaminocarbonyl(e.g., methanesulfonylaminocarbonyl, ethanesulfonylaminocarbonyl, etc.),acylaminosulfonyl (e.g., acetoamidesulfonyl, methoxyacetoamidesulfonyl,etc.), acylaminocarbonyl (e.g., acetoamidecarbonyl,methoxyacetoamidecarbonyl, etc.), and sulfinylaminocarbonyl (e.g.,methanesulfinylaminocarbonyl, ethanesulfinylaminocarbonyl, etc.). Amongthe groups exemplified above, the preferred are vinyl, aryl, aheterocycle, cyano, sulfonyl, acyl, ureido, thioureido, alkylthio,heterocyclic thio, carbonyloxy, acylamino, thioamide, carboxy, hydroxy,mercapto, carbamoyl, sulfamoyl, sulfonamide and acylaminocarbonyl, andthe more preferred are vinyl, aryl, cyano, acyl, alkylthio, carbonyloxy,acylamino and hydroxy.

[0034] Further, R₁ and L₁₁, and R₂ and L₁₄ can bond with each other toform a 5- or 7-membered cyclic structure, respectively.

[0035] Ar₁ and Ar₂ represent each independently aryl or a heterocycle.Aryl includes substituted and unsubstituted aryl groups including, forexample, phenyl, 2-naphthyl, 1-naphthyl, o-tolyl, o-methoxyphenyl,m-chlorophenyl, m-bromophenyl, p-tolyl, p-ethoxyphenyl and the like. Theheterocycle includes substituted and unsubstituted heterocyclesincluding, for example, 2-furyl, 5-methyl-2-furyl, 2-thienyl,2-imidazolyl, 2-methyl-1-imidazolyl, 4-phenyl-2-thiazolyl,5-hydroxy-2-benzothiazolyl, 2-pyridyl, 1-pyrrolyl and the like. Theabove-recited groups can include the substituents as exemplified for R₁and R₂ in the above. Among the groups described above, the preferred isaryl, and the more preferred is phenyl.

[0036] In the general formula (1), when a group having electric chargesof either cations or anions has been substituted, pairing ions areformed from the equivalent of the cations or the anions so that theelectric charges in the molecules are offset. For example, in case ofions required to offset the electric charges in the moleculesrepresented by X₁₁, examples of the cation include specifically protons,organic ammonium ions (e.g., ions of each of triethylammonium,triethanolammonium, pyridinium, etc.), and inorganic cations (e.g.,cations of each of lithium, sodium, potassium, etc.), and examples ofthe acid anions include specifically halogen ions (e.g., chlorine ions,bromine ions, iodine ions, etc.), p-toluenesulfonic acid ions,perchloric acid ions, boron tetrafluoride ions, sulfuric acid ions,methylsulfuric acid ions, ethylsulfuric acid ions, methanesulfonic acidions, trifluoromethanesulfonic acid ions, hexafluorophophoric acid ionsand the like. In the formula (1), n denotes the number of ions requiredfor offsetting the electric charges in the molecules.

[0037] The photothermographic imaging material of the inventioncomprises at least one of compounds represented by the above generalformula (2).

[0038] In the general formula (2), L₂₁ to L₂₄ represent eachindependently hydrogen, a halogen atom, amino, alkylthio, arylthio,lower alkyl, lower alkoxy, aryloxy, aryl or a heterocycle, where thehalogen atom includes fluorine, chlorine, bromine and iodine; aminoincludes substituted or unsubstituted, that is, for example, amino,dimethylamino, diphenylamino and methylphenylamino; alkylthio includes,for example, methylthio, ethylthio, benzylthio; arylthio includessubstituted or unsubstituted arylthio groups, that is, for example,phenylthio and m-fluorophenylthio; the lower alkyl includesstraight-chain or branched alkyl groups each containing carbon atoms notmore than 5, that is specifically methyl, ethyl, propyl, butyl, pentyl,isopropyl and the like; the lower alkoxy includes alkoxy groups eachcontaining carbon atoms not more than 4, that is specifically methoxy,ethoxy, propoxy, isopropoxy and the like; aryloxy includes substitutedand unsubstituted aryloxy groups, that is specifically phenoxy,p-tolyloxy, m-carboxyphenyloxy and the like; aryl includes substitutedand unsubstituted aryl groups, that is, for example, phenyl, 2-naphthyl,1-naphthyl, o-tolyl, o-methoxyphenyl, m-chlorophenyl, m-bromophenyl,p-tolyl, and p-ethoxyphenyl; and the heterocyclic group includessubstituted and unsubstituted heterocycles, that is, for example,2-furyl, 5-methyl-2-furyl, 2-thienyl, 2-imidazolyl,2-methyl-1-imidazolyl, 4-phenyl-2-thiazolyl, 5-hydroxy-2-benzothiazolyl,2-pyridyl and 1-pyrrolyl. Any of the above-exemplified groups can have asubstituent such as phenyl, halogen, alkoxy and hydroxy. It ispreferable for L₂₁ to L₂₄ to be hydrogen, lower alkyl, aryl or aheterocycle, and more preferably hydrogen, methyl or phenyl.

[0039] L₂₁ and L₂₂, L₂₂ and L₂₃ and L₂₃ and L₂₄ can bond with each otherrespectively, to form a 5- to 7-membered ring, where L₂₁ to L₂₄ eachrepresent a nonmetal atom required for forming a 5- to 7-membered ring.Examples of the 5- to 7-membered rings include, for example, acyclopentene ring, a cyclohexene ring, a cycloheptene ring, a decalinring and the like. These rings can be substituted with lower alkyl,lower alkoxy or aryl, those which are exemplified for L₂₁ to L₂₄ in theabove. It is preferable for the 5- to 7-membered ring to be acyclopentene ring or a decalin ring, and more preferably a decalin ring.

[0040] R₃ and R₄ represent each independently an aliphatic group.Examples of the aliphatic group include, for example, branched orstraight-chain alkyl containing 1 to 30 carbon atoms (e.g., methyl,ethyl, propyl, butyl, pentyl, isopentyl, 2-ethylhexyl, octyl, decyl andthe like), alkenyl containing 3 to 30 carbon atoms (e.g.., 2-propenyl,3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl,4-hexenyl and the like), and aralkyl containing 7 to 30 carbon atoms(e.g., benzyl, phenetyl and the like). It is preferable for thealiphatic group to be branched or straight-chain alkyl containing 1 to20 carbon atoms or alkenyl containing 3 to 20 carbon atoms.

[0041] The above-described aliphatic groups can further includesubstituents, and examples of such substituents are same as thoseexemplified for R₁ and R₂ in the general formula (1).

[0042] Furthermore, R₃ and L₂₁, and R₄ and L₂₄ can bond with each other,respectively, to form a 5- or 7-membered cyclic structure.

[0043] In the general formula (2), when a group having electric chargesof either cations or anions has been substituted, pairing ions areformed from the equivalent of the cations or the anions so that theelectric charges in the molecules are offset. For example, in case ofions required to offset the electric charges in the moleculesrepresented by X₂₁, examples of the cation include specifically protons,organic ammonium ions (e.g., ions of each of triethylammonium,triethanolammonium, pyridinium, etc.), and inorganic cations (e.g., ionsof each of lithium, sodium, potassium, etc.), and examples of the acidanions include specifically halogen ions (e.g., chlorine ions, bromineions, iodine ions, etc.), p-toluenesulfonic acid ions, perchloric acidions, boron tetrafluoride ions, sulfuric acid ions, methylsulfuric acidions, ethylsulfuric acid ions, methanesulfonic acid ions,trifluoromethanesulfonic acid ions, hexafluorophophoric acid ions andthe like. In the formula (2), m denotes the number of ions required foroffsetting the electric charges in the molecules.

[0044] R₂₁ to R₂₄ represent each independently hydrogen, alkyl or aryl,where, specifically, alkyl is preferably alkyl containing 1 to 10 carbonatoms. Specific examples of alkyl include methyl, ethyl, propyl,isopropyl, butyl, t-butyl, pentyl, neo-pentyl, 2-ethylhexyl, octyl,decyl, cyclohexyl, cycloheptyl, 1-methylcyclohexyl, ethenyl-2-propenyl,3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl,1-cycloalkenyl, 2-cycloalkenyl, ethynyl, 1-propynyl and the like.Specific examples of aryl include phenyl, naphthyl, anthranil and thelike. It is preferable for R₂₁ to R₂₄ to be hydrogen or alkyl, and morepreferably hydrogen or methyl.

[0045] The above-described groups can further include substituents.Examples of such substituents include the same substituents exemplifiedfor R₁ and R₂ in the general formula (1) in the above.

[0046] R₂₅ to R₃₂ represent groups capable of being substituted to abenzene ring. Specific examples of such groups include alkyl (e.g.,methyl, ethyl, butyl, isobutyl, etc.), aryl (including monocyclic andpolycyclic aryl groups, for example, phenyl, carboxyphenyl, p-tolyl,p-butylphenyl, naphthyl, etc.), a heterocycle (for example, any oftetrahydrofuryl, 2-pyrrolidinone-1-yl, thienyl, furyl, pyridyl,carbazolyl, pyrrolyl, indolyl, etc.), a halogen atom (for example,fluorine, chlorine, bromine, etc.), vinyl, trifluoromethyl, alkoxy (forexample, methoxy, ethoxy, methoxyethoxy, etc.), aryloxy (for example,phenoxy, p-tolyloxy, etc.), sulfonyl (for example, methanesulfonyl,p-toluenesulfonyl, etc.), alkoxycarbonyl (for example, ethoxycarbonyl,butoxycarbonyl, etc.), amino (for example, amino, biscarboxymethylamino,etc.), acyl (for example, acetyl, benzoyl, etc.), ureido (for example,ureido, 3-methylureido, 3-phenylureido, etc.), thioureido (for example,thioureido, 3-methylthioureido, etc.), alkylthio (for example,methylthio, ethylthio, etc.), arylthio (for example, phenylthio, etc.),sulfinyl (for example, methanesulfinyl, ethanesulfinyl, phenylsulfinyl,etc.), hydroxy, styryl, and acylamino (for example, acetylamino,benzoylamino, etc.). Furthermore, the groups exemplified above canfurther have a substituent of any of these groups. The preferred groupsfor R₂₅ to R₃₂ is alkyl, aryl, a heterocycle, a halogen atom, alkylthio,arylthio or sulfinyl, and more preferred is sulfinyl. Besides, R₂₅ andR₂₆, R₂₆ and R₂₇, R₂₇ and R₂₈, R₂₉ and R₃₀, R₃₀ and R₃₁ and R₃₁ and R₃₂can bond with each other, respectively, to form a cyclic structure. Notethat, however, R₂₇ is neither aryl nor a heterocycle.

[0047] In the photothermographic imaging material of the invention, thecompound represented by the above general formula (1) is the compoundrepresented by the above formula (3).

[0048] In the general formula (3), L₁₁ to L₁₇ are synonymous with L₁₁ toL₁₇ in the general formula (1). Also, R₁ and R₂ are synonymous with R₁and R₂ in the general formula (1).

[0049] Similarly, X₁l is synonymous with X₁₁ in the general formula (1),and n is synonymous with n in the general formula (1).

[0050] Ar₃ and Ar₄ represent each independently aryl, and examples ofthis aryl include substituted and unsubstituted aryl groups, that isphenyl, 2-naphthyl, 1-naphthyl, o-tolyl, o-methoxyphenyl,m-chlorophenyl, m-bromophenyl, p-tolyl, p-ethoxyphenyl and the like. Thepreferred for Ar₃ and Ar₄ are phenyl.

[0051] In the photothermographic imaging material of the invention, thecompound represented by the above general formula (1) is the compoundrepresented by the above formula (4).

[0052] In the general formula (4), L₁₁ to L₁₇ are synonymous with L₁₁ toL₁₇ in the general formula (1). Also, R₁ and R₂ are synonymous with R₁and R₂ in the general formula (1).

[0053] Similarly, X₁₁ is synonymous with X₁₁ in the general formula (1),and n is synonymous with n in the general formula (1).

[0054] In the photothermographic imaging material of the invention, thecompound represented by the above general formula (1) is the compoundrepresented by the above formula (5).

[0055] In the general formula (5), L₁l to L₁₄ are synonymous with L₁₁ toL₁₄ in the general formula (1). Also, R₁ and R₂ are synonymous with R₁and R₂ in the general formula (1).

[0056] Similarly, X₁₁ is synonymous with X₁₁ in the general formula (1),and n is synonymous with n in the general formula (1).

[0057] R₃₁ to R₃₄ represent each independently hydrogen, alkyl or aryl.Specifically, it is preferable for the alkyl to be alkyl containing 1 to10 carbon atoms. Specific examples of R₃₁ to R₃₄ include methyl, ethyl,propyl, isopropyl, butyl, t-butyl, pentyl, neo-pentyl, 2-ethylhexyl,octyl, decyl, cyclohexyl, cycloheptyl, 1-methylcyclohexyl,ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl,1-methyl-3-butenyl, 1-cycloalkenyl, 2-cycloalkenyl, ethynyl, 1-propynyland the like. Specific examples of aryl include phenyl, naphthyl,anthranil and the like. The above-exemplified groups can include furthersubstituents, and examples of such substituents are synonymous with R₁and R₂ in the general formula (1). The preferred for R₃₁ to R₃₄ ishydrogen, methyl or phenyl, and more preferred is hydrogen.

[0058] In the photothermographic imaging material of the invention, thecompound represented by the above general formula (1) is the compoundrepresented by the above formula (6).

[0059] In the general formula (6), L₂₁ to L₂₄ are synonymous with L₂₁ toL₂₄ in the general formula (2). Also, R₃ and R₄ are synonymous with R₃and R₄ in the general formula (2).

[0060] Similarly, X₂₁ is synonymous with X₂₁ in the general formula (2),and m is synonymous with m in the general formula (2). Also, R₂₁ to R₂₄are synonymous with R₂₁ to R₂₄ in the general formula (2).

[0061] R₄₁ and R₄₂ represent each independently unsubstituted loweralkyl, cycloalkyl, aralkyl, aryl or a heterocycle. The unsubstitutedlower alkyl is a straight-chain or branched alkyl containing carbonatoms not more than 5, that is specifically methyl, ethyl, propyl,butyl, pentyl, isopropyl, or the like. Examples of cycloalkyl include,cyclopropyl, cyclobutyl, cyclopentyl, and the like. Examples of aralkylinclude, benzyl, phenetyl, p-methoxyphenylmethyl,o-acetylaminophenylethyl and the like. Examples of aryl includesubstituted and unsubstituted aryl groups, such as phenyl, 2-naphthyl,1-naphthyl, o-tolyl, o-methoxyphenyl, m-chlorophenyl, m-bromophenyl,p-tolyl, p-ethoxyphenyl and the like. Examples of the heterocycleinclude substituted and unsubstituted heterocycles, such as 2-furyl,5-methyl-2-furyl, 2-thienyl, 2-imidazolyl, 2-methyl-1-imidazolyl,4-phenyl-2-thiazolyl, 5-hydroxy-2-benzothiazolyl, 2-pyridyl, 1-pyrrolyland the like. The above-exemplified groups can further havesubstituents, such as phenyl, halogen, alkoxy, hydroxy and the like. Thepreferred for R₄₁ and R₄₂ is unsubstituted lower alkyl or aryl, and themore preferred is methyl, ethyl or phenyl.

[0062] The specific examples of the compound represented by the generalformulas (1) and (3) are exemplified below. However, it should be notedthat the present invention is not limited to the compounds exemplifiedthereto.

[0063] Specific examples of the compounds represented by the generalformulas (2) and (4) are exemplified below. However, it should be notedthat the present invention is not limited to the compounds thereto.

[0064] The compounds (herein, also referred to as either infraredsensitizing colorants or sensitizing colorants) represented by thegeneral formulas (1) to (6) according to the present invention can beeasily synthesized according to the processes described in, for example,F. M. Harmer, The Chemistry of Heterocyclic Compounds, Vol. 18; TheCyanine Dyes and Related Compounds (Edited by A. Weissberger, Publishedby Interscience Inc., New York 1964); J. Ber., 64, 1664-1674 (1931);Ukrain. Khim. Zhur., 21, 744-749 (1955); and specifications of UK PatentNo. 625,245; UK Patent No. 895,930; U.S. Pat. No. 2,320,439; and U.S.Pat. No. 2,398,999.

[0065] The time to add any of these infrared sensitizing colorants canbe set at any stage following to the preparation of silver halide. Forexample, the infrared sensitizing colorant can be added in the state ofsolution in a solvent or in so-called solid-state dispersion state inwhich the colorant is dispersed in particulates to photosensitiveemulsion containing either silver halide particles or a mixture ofsilver halide particles and organic silver salt particles.Alternatively, it is possible to add the infrared sensitizing colorantto silver halide particles prior to chemical sensitization to render thesilver halide particles to absorb the colorant and then apply thechemical sensitization similarly to the case of a compound containinghetero atoms that has adsorption property to the silver halide. Withsuch an application of chemical sensitization, it is possible to preventthe central core of the chemical sensitization from its dispersion andto achieve high photosensitivity and less fogging.

[0066] The sensitizing colorant is contained in the emulsion of silverhalide at a rate in total of from 1×10⁻⁶ to 5×10⁻³ mol, preferably from1×10⁻⁵ to 2.5×10⁻³ mol, and more preferably from 4×10⁻⁵ to 1×10⁻³ mol,relative to 1 mol of silver halide in both cases that the sensitizingcolorant is used alone and it is used in combination.

[0067] The photothermographic imaging material according to the presentinvention contains a compound represented by the general formula (7).The compound represented by the general formula (7) is a reducing agentof silver ions, and it is particularly prefered that the compound is abisphenol derivative.

[0068] The general formula (7) is described in detail.

[0069] In the general formula (7), R₁₁ and R₁₂ each independentlyrepresents hydrogen, a 3- to 10-membered nonaromatic cyclic group or a5- or 6-membered aromatic cyclic group. Concrete examples of the 3- to10-membered nonaromatic group include 3-membered cyclic groups, such ascyclopropyl, aziridyl and oxiranyl; 4-membered cyclic groups, such ascyclobutyl, cyclobutenyl, oxetanyl and azetidinyl; 5-membered cyclicgroups, such as cyclopentyl, cyclopentenyl, cyclopentadienyl,tetrahydrofuranyl, pyrrolidinyl and tetrahydrothienyl; 6-membered cyclicgroups, such as cyclohexyl, cyclohexenyl, cyclohexadienyl,tetrahydropyranyl, pyranyl, piperidinyl, dioxanyl,tetrahydrothiopyranyl, norcaranyl, norpinanyl and norbornyl; 7-memberedcyclic groups, such as cycloheptyl, cycloheptynyl and cycloheptadienyl;8-membered cyclic groups, such as cyclooctanyl, cyclooctenyl,cyclooctadienyl and cyclooctatrienyl; 9-membered cyclic groups, such ascyclononanyl, cyclononenyl, cyclononadienyl and cyclononatrienyl; and10-membered cyclic groups, such as cyclodecanyl, cyclodecaenyl,cyclodecadienyl and cyclodecatrienyl.

[0070] The preferred are 3- to 6-membered nonaromatic cyclic groups, andmore preferably 5- or 6-membered nonaromatic cyclic groups, and amongthose which, hydrocarbon rings containing no hetero atom areparticularly preferred. The nonaromatic cyclic group can bond with theother ring through spiro atoms to form spiro bonds, or can be condensedin any manner with any of other rings including aromatic rings to form aring. Further, the nonaromatic cyclic group can be substituted witharbitrary substituents on the ring. Note that the above hydrocarbon ringpreferably includes therein an alkenyl skeleton or an alkynyl skeletonincluding bondings, such as —C═C— and —C≡C—.

[0071] Specific examples of the substituent include halogen atom, e.g,fluorine atom, chlorine atom and bromine atom; alkyl, e.g., methyl,ethyl, propyl, butyl, pentyl, isopentyl, 2-ethylhexyl, octyl and decyl;cycloalkyl, e.g., cyclohexyl and cycloheptyl; alkenyl, e.g.,ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl and1-methyl-3-butenyl; cycloalkenyl, e.g., 1-cycloalkenyl and2-cycloalkenyl; alkynyl, e.g., ethynyl and 1-propinyl; alkoxy, e.g.,methoxy, ethoxy and propoxy; alkylcarbonyloxy, e.g., acetyloxy;alkylthio, e.g., methylthio and trifluoromethythio; carboxyl;alkylcarbonylamino, e.g., acetylamino; ureido, e.g.,methylaminocarbonylamino; alkylsulfonylamino, e.g.,methanesulfonylamino; alkylsulfonyl, e.g., methanesulfonyl andtrifluoromethanesulfonyl; carbamoyl, e.g., carbamoyl,N,N-dimethylcarbamoyl and N-morpholinocarbonyl; sulfamoyl, e.g.,sulfamoyl, N,N-dimethylsulfamoyl and morpholinosulfamoyl;trifluoromethyl; hydroxyl; nitro; cyano; alkylsulfonamide, e.g.,methanesulfonamide and butanesulfonamide; alkylamino, e.g., amino,N,N-dimethylamino and N,N-diethylamino; sulfo; phosphono; sulfite;sulfino; alkylsulfonylaminocarbonyl, e.g., methanesulfonylaminocarbonyland ethanesulfonylaminocarbonyl; alkylcarbonylaminosulfonyl, e.g.,acetoamidesulfonyl and methoxyacetoamidesulfonyl; alkynylaminocarbonyl,e.g., acetoamidecarbonyl and methoxyacetoamidecarbonyl;alkylsulfinylaminocarbonyl, e.g., methanesulfinylaminocarbonyl andethanesulfinylaminocarbonyl; and the like. When the nonaromatic cyclicgroup is substituted by 2 or more substituents, they can be the same ordifferent from one another. The particularly preferred substituent isalkyl.

[0072] The 5- or 6-membered aromatic cyclic group represented by R₁₁ andR₁₂ can include a single ring or a condensed ring, and the preferred arearomatic mono- or bicarbocycles containing 6 to 30 carbon atoms, e.g.,benzene ring, naphthalene ring and the like. Among the carbocyclesmentioned above, the one preferably used is benzene ring. The aromatichetero ring preferably used is a 5- or 6-membered aromatic hetero ringthat can include a condensed ring. A 5-membered aromatic hetero ringthat can include a condensed ring is more preferably used. Examples ofsuch a hetero ring preferably used include imidazole, pyrazole,thiophene, furan, pyrrole, pyridine, pyrimidine, pyrazine, pyridazine,triazole, triazine, indole, indazole, purine, thiadiazole, oxadiazole,quinoline, phthalazine, naphthylidine, quinoxaline, quinazoline,cinnoline, pteridine, acridine, phenanthroline, phenazine, tetrazole,thiazole, oxazole, benzimidazole, benzoxazole, benzothiazole,indolenine, and tetrazaindene, and the ones more preferably used areimidazole, pyrazole, thiophene, furan, pyrrole, triazole, thiadiazole,tetrazole, thiazole, benzimidazole and benzothiazole, and the onesparticularly preferably used are thiophene, furan and thiazole. Theabove-enumerated hetero rings can be condensed with the other ringsincluding aromatic rings in any manner. Further, the hetero ringsdescribed above can be substituted with arbitrary substituents. As suchsubstituents, the same substituents described above for the 3- to10-membered nonaromatic cyclic group can be given.

[0073] It will be the most preferable combination when R₁₁ is a5-membered aromatic heterocycle and R₁₂ is hydrogen.

[0074] R₁₃ and R₁₄ each represent hydrogen, alkyl, alkynyl, aryl or aheterocycle. Specifically, the alkyl is preferably an alkyl containing 1to 10 carbon atoms. Concrete examples of the alkyl include methyl,ethyl, propyl, isopropyl, butyl, t-butyl, pentyl, isopentyl,2-ethylhexyl, octyl, decyl, cyclohexyl, cycloheptyl, 1-methylcyclohexyl,ethenyl-2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl,1-methyl-3-butenyl, 1-cycloalkenyl, 2-cycloalkenyl, ethynyl, 1-propynyland the like. R₁₃ is preferably methyl, ethyl, isopropyl, t-butyl,cyclohexyl, 1-methylcyclohexyl and the like, and more preferably methyl,t-butyl, 1-methylcyclohexyl and the like, and the most preferablyt-butyl and 1-methylcyclohexyl. R₁₄ is preferably methyl, ethyl,isopropyl, t-butyl, cyclohexyl, 1-methylcyclohexyl, 2-hydroxyethyl andthe like, and more preferably methyl and 2-hydroxyethyl. Preferredexamples of the aryl represented by R₁₃ and R₁₄ include, concretely,phenyl, naphthyl, anthranil and the like. Concrete examples of theheterocycle represented by R₁₃ and R₁₄ include aromatic heterocycles,such as pyridine, quinoline, isoquinoline, imidazole, pyrazole,triazole, oxazole, thiazole, oxadiazole, thiadiazole and tetrazole, andnonaromatic heterocycles, such as piperidino, morpholino,tetrahydrofuryl, tetrahydrothienyl and tetrahydropyranyl. Thesesubstituents enumerated above can have substituents, and theabove-described substituents to be substituted onto the ring of thenonaromatic cyclic group can be given as the examples of the substituentdescribed hereinabove.

[0075] When both R₁₁ and R₁₂ are hydrogen, the most preferablecombination thereof will be obtained with a tertiary alkyl, e.g.,t-butyl, 1-methylhexyl, etc., for R₁₃, and primary alkyl, e.g., methyl,2-hydroxyethy, etc., for R₁₄.

[0076] Q represents a substituent that can be substituted on the benzenering. Concrete examples of Q include alkyl containing 1 to 25 carbonatoms, e.g., methyl, ethyl, propyl, isopropyl, t-butyl, pentyl, hexyl,cyclohexy and the like; halogenated alkyl, e.g., trifluoromethyl,perfluorooctyl and the like; cycloalkyl, e.g., cyclohexyl, cyclopentyland the like; alkynyl. e.g., propargyl and the like; glycidyl; acrylate;metacrylate; aryl, e.g., phenyl; heterocycles, e.g., pyridine,thiazolyl, oxazolyl, imidazolyl, furyl, pyrrolyl, pyrazinyl,pyrimidinyl, pyridazinyl, selenazolyl, sulforanyl, piperidinyl,pyrazolyl, tetrazolyl and the like; halogen atom, e.g., chlorine atom,,bromine atom, iodine atom, fluorine atom and the like; alkoxy, e.g.,methoxy, ethoxy, propyloxy, pentyloxy, cyclopentyloxy, hexyloxy,cyclohexyloxy and the like; aryloxy, e.g., phenoxy and the like;alkoxycarbonyl, e.g., methyloxycarbonyl, ethyloxycarbonyl,butyloxycarbonyl and the like; aryloxycarbonyl, e.g., phenyloxycarbonyland the like; sulfonamide, e.g., methanesulfonamide, ethanesulfonamide,butanesulfonamide, hexanesulfonamide, cyclohexanesulfonamide,benzenesulfonamide and the like; sulfamoyl, e.g., aminosulfonyl,methylaminosulfonyl, dimethylaminosulfohyl, butylaminosulfonyl,hexylaminosulfonyl, cyclohexylaminosulfonyl, phenylaminosulfonyl,2-pyridylaminosulfonyl and the like; urethane, e.g., methylureido,ethylureido, pentylureido, cyclohexylureido, phenylureido,2-pyridylureido and the like; acyl, e.g., acetyl, propionyl, butanoyl,hexanoyl, cyclohexanoyl, benzoyl, pyrizinoyl and the like; carbamoyl,e.g., aminocarbonyl, methylaminocarbonyl, dimethylaminocarbonyl,propylaminocarbonyl, pentylaminocarbonyl, cyclohexylaminocarbonyl,phenylaminocarbonyl, 2-pyridylaminocarbonyl and the like; amide, e.g.,acetoamide, propionamide, butaneamide, hexaneamide, benzamide and thelike; sulfonyl, e.g., methylsulfonyl, ethylsulfonyl, butylsulfonyl,cyclohexylsulfonyl, phenylsulfonyl, 2-pyridylsulfonyl and the like;amino, e.g., amino, ethylamino, dimethylamino, butylamino,cyclopentylamino, anilino, 2-pyridylamino and the like; cyano; nitro;sulfo; carboxyl; hydroxyl; oxamoyl and the like. Further, the groupsenumerated above can be substituted by any of themselves. In the generalformula (7), n denotes 0 or an integer of 1 or 2, but it is the mostpreferable when n is 0. When a plurality of Q are substituted, they canbe same or different from one another.

[0077] The amount of the silver ion reducing agent used for the thermaldevelopment photosensitive material according to the present inventionvaries depending on the types of the organic silver salt and thereducing agent and the other additives. However, in general, it isappropriate that the amount of the silver ion reducing agent is 0.05 to10 mol, and preferably 0.1 to 3 mol, relative to 1 mol of the organicsilver salt. If the amount in total is in the above-defined range, 2 ormore types of silver ion reducing agents according to this invention canbe used in combination. In the present invention, there can be apreferable case that the reducing agent can be added into thephotosensitive emulsion solution comprising the photosensitive silverhalide, the organic silver salt particles and a solvent, and it is mixedjust before coating the photosensitive emulsion solution, immediatelyfollowed by the coating of the emulsion solution added with the reducingagent. In such a case, variation in the photographic performance to becaused during the stationary period can be favorably reduced sometime.

[0078] The photothermographic imaging material according to the presentinvention contains a silver ion reducing agent. In the presentinvention, known reducing agents can be used in combination with abisphenol compound represented by the general formula (7) according tothe present invention, and such known reducing agents are described in,for example, U.S. Pat. Nos. 3,770,448, 3,773,512 and 3,593,863, RD 17029and 29963, and the like. Among the reducing agents, bisphenol compounds,particularly hindered phenols bonded with branched alkylene chains, arepreferable to use.

[0079] In the following, the representative examples of the preferredcompounds represented by the general formula (7) are given. However, itshould be noted that the bisphenol compounds according to this inventionare not limited to the examples given below.

[0080] Note that, in the thermal development photography photosensitivematerial according to the present invention, a sensitizing agentrepresented by the general formulae (11) and (12) shown below can becontained instead of the compound represented by the general formula(1), or in addition thereto. Now, the sensitizing agents represented bythe general formulae (11) and (12) will be described in the following.

[0081] Wherein Y₁ and Y₂ represent each independently oxygen atom,selenium atom or —CH═CH— group; L₁ to L₉ represent each independentlymethine group; R₁ and R₂ each represent aliphatic group; R₃, R₄, R₂₃ andR₂₄ each represent lower alkyl, cycloalkyl, alkenyl, aralkyl, aryl orheterocylic group. W₁, W₂, W₃ and W₄ each represent hydrogen atom, asubstituent or non-metal atom group required for bonding W₁ and W₂, andW₃ and W₄ respectively to form a condensed ring, or R₃, R₄, R₂₃, R₂₄,W₁, W₂, W₃ and W₄ each represent a non-metal atom group required forbonding R₃ and W₁, R₃ and W₂, R₂₃ and W₁, R₂₃ and W₂, R₄ and W₄, R₂₄ andW₃, and R₂₄ and W₄ respectively to form a 5- or 6-membered condensedring; X₁ represents an ion required for offsetting electric charge inthe molecule, and kl represents the number of ions required foroffsetting the electric charge in the molecule; m1 represent 0 or 1; andn1 and n2 each represent 0 or an integer of 1 or 2, and at least one ofn1 and n2 is not 0.

[0082] Example of an aliphatic group represented by R₁ and R₂ in thegeneral formulae (11) and (12) include, for example, branched orstraight-chain alkyl containing 1 to 10 carbon atoms, e.g., methyl,ethyl, propyl, butyl, pentyl, isopentyl, 2-ethylhexyl, octyl, decyl andthe like; alkenyl containing 3 to 10 carbon atoms, e.g., 2-propenyl,3-butenyl, 1-methyl-3-propenyl, 3-pentenyl, 1-methyl-3-butenyl,4-hexenyl and the like; and aralkyl containing 7 to 10 carbon atoms,e.g., benzyl, phenethyl and the like. The above-enumerated groups canfurther have a substitutent of hydrophilic groups including, loweralkyl, e.g., methyl, ethyl, propyl and the like; halogen atom, e.g.,fluorine atom, chlorine atom, bromine atom and the like; vinyl; aryl,e.g., phenyl, p-tolyl, p-bromophenyl and the like; trifluoromethyl;alkoxy, e.g., methoxy, ethoxy, methoxyethoxy and the like; aryloxy,e.g., phenoxy, p-tolyloxy and the like; cyano; sulfonyl, e.g.,methanesulfonyl, trifluoromethanesulfonyl, p-toluenesulfonyl and thelike; alkoxycarbonyl, e.g., ethoxycarbonyl, butoxycarbonyl and the like;amino, e.g., amino, biscarboxymethylamino and the like; aryl, e.g.,phenyl, carboxyphenyl and the like; heterocycles, e.g.,tetrahydrofurfuryl, 2-pyrrolidinone-1-yl and the like; acyl, e.g.,acetyl, benzoyl and the like; ureido, e.g., ureido, 3-methylureido,3-phenylureido and the like; thioureido, e.g., thioureido,3-methylthioureido and the like; alkylthio, e.g., methylthio, ethylthioand the like; arylthio, e.g., phenylthio and the like; heterocyclicthio, e.g., 2-thienylthio, 3-thienylthio, 2-imdazolylthio and the like;carbonyloxy, e.g., acetyloxy, propanoyloxy, benzoyloxy and the like;acylamino, e.g., acetylamino, benzoylamino and the like; thioamide,e.g., thioacetoamide, thiobenzoylamino and the like; sulfo; carboxy;phosphono; sulfato; hydroxy; mercapto; sulfino; carbamoyl, e.g.,carbamoyl, N-methylcarbamoyl, N,N-tetramethylenecarbamoyl and the like;sulfamoyl, e.g., sulfamoyl, N,N-3-oxapentamethyleneaminosulfonyl and thelike; sulfonamide, e.g., methanesulfonamide, butanesulfonamide and thelike; sulfonylaminocarbonyl, e.g., methanesulfonylaminocarbonyl,ethanesulfonylaminocarbony and the like; acylaminosulfonyl, e.g.,acetoamidesulfonyl, methoxyacetoamidesulfonyl and the like;acylaminocarbonyl, e.g., acetoamidecarbonyl, methoxyacetoamidecarbonyland the like; sulfinylaminocarbonyl, e.g, methanesulfinylaminocarbonyl,ethanesulfinylaminocarbonyl and the like. Concrete examples of thealiphatic group having at least one substituent of the above-enumeratedhydrophilic groups include carboxymethyl, carboxyethyl, carboxybutyl,carboxypentyl, 3-sulfatobutyl, 3-sulfopropyl, 2-hydroxy-3-sulfopropyl,4-sulfobutyl, 5-sulfopentyl, 3-sulfopentyl, 3-sulfinobutyl,3-phosphonopropyl, hydroxyethyl, N-methanesulfonylcarbamoylmethyl,2-carboxy-2-propenyl, o-sulfobenzyl, p-sulfophenetyl, p-carboxybenzyland the like.

[0083] The concrete examples of groups represented by R₃, R₄, R₂₃ andR₂₄ in the general formulas (11) and (12) include a straight-chain orbranched lower alkyl group containing not more than 5 carbon atoms suchas, ethyl, propyl, butyl, pentyl, isopropyl and the like; cycloalkylsuch as cyclopropyl, cyclobutyl, cyclopentyl and the like; alkenyl suchas 2-propenyl, 3-butenyl, 1-methyl-3-propenyl, 3-pentenyl,1-methyl-3-butenyl, 4-hexenyl and the like; aralkyl such as benzyl,phenetyl, p-methoxyphenylmethyl, o-acetylaminophenylethyl and the like;aryl such as phenyl, 2-naphthyl, 1-naphthyl, o-tolyl, o-methoxyphenyl,m-chlorophenyl, m-bromophenyl, p-tolyl, p-ethoxyphenyl and the like; andsubstituted and unsubstituted heterocycles such as 2-furyl,5-methyl-2-furyl, 2-thienyl, 3-thienyl, 2-imidazolyl,2-methyl-1-imidazolyl, 4-phenyl-2-thiazolyl, 5-hydroxy-2-benzothiazolyl,2-pyridyl, 1-pyrrolyl and the like. The respective groups enumeratedabove can further have at least one substituent of lower alkyl, e.g.,methyl, ethyl and like; lower alkoxy, e.g., methoxy, ethoxy and thelike; hydroxy; halogen atom, e.g., fluorine atom, chlorine atom, bromineatom, iodine atom and the like; aryl, e.g., phenyl, tolyl, chloroethyl,chlorophenyl and the like; mercapto; lower alkylthio, e.g., methylthio,ethylthio and the like. The particularly preferred for the substituentsto be substituted to the groups represented by R₃, R₄, R₂₃ and R₂₄ are agroup of nonmetal atoms those which are necessary for the respectivepairs of R₃ and W₁, R₃ and W₂, R₂₃ and W₁, R₂₃ and W₂, R₄ and W₄, R₂₄and W₃, and R₂₄ and W₄ to bond with each other to form 5- or 6-memberedcondensed rings.

[0084] Concrete examples of the substituents respectively represented byW₁ to W₄ include alkyl, e.g., methyl, ethyl, butyl, isobutyl and thelike; monocyclic and multicyclic aryl groups, e.g., phenyl, naphthyl andthe like; heterocycles, e.g., thienyl, furyl, pyridyl, carbazolyl,pyrrolyl, indolyl and the like; halogen atom, e.g., fluorine atom,chlorine atom, bromine atom and the like; vinyl; aryl, e.g., phenyl,p-tolyl, p-bromophenyl and the like; trifluoromethyl; alkoxy, e.g.,methoxy, ethoxy, methoxyethoxy and the like; aryloxy, e.g., phenoxy,p-tolyloxy and the like; sulfonyl, e.g., methanesulfonyl,p-toluenesulfonyl and the like; alkoxycarbonyl, e.g., ethoxycarbonyl,butoxycarbonyl and the like; amino, e.g., amino, biscarboxymethylaminoand the like; aryl, e.g., phenyl, carboxyphenyl and the like;heterocycles, e.g., tetrahydrofurfuryl, 2-pyrrolidinone-1-yl and thelike; acyl, e.g., acetyl, benzoyl and the like; ureido, e.g., ureido,3-methylureido, 3-phenylureido and the like; thioureido, e.g.,thioureido, 3-methylthioureido and the like; alkylthio, e.g.,methylthio, ethylthio and the like; arylthio, e.g., phenylthio and thelike; hydroxy; styryl and the like.

[0085] The substituents enumerated above can have a substituentrepresented by R₁ and the like exampled above for the aliphatic groups.Concrete examples of the substituted alkyl include 2-methoxyethyl,2-hydroxyethyl, 3-ethoxycarbonylpropyl, 2-carbamoylethyl,2-methanesulfonylethyl, 3-methanesulfonylaminopropyl, benzyl, phenetyl,carboxymethyl, carboxyethyl, allyl, 2-furylethyl and the like. Concreteexamples of the substituted aryl include p-carboxyphenyl,p-N,N-dimethylaminophenyl, p-morpholinophenyl, p-methoxyphenyl,3,4-dimethoxyphenyl, 3,4-methylenedioxyphenyl, 3-chlorophenyl,p-nitrophenyl and the like. Concrete examples of the substitutedheterocycle include 5-chloro-2-pyridyl, 5-ethoxycarbonyl-2-pyridyl,5-carbamoyl-2-pyridyl and the like.

[0086] The saturated or unsaturated condensed rings which is formed bythe respective bondings of W₁ and W₂, W₃ and W₄, R₃ and W₁, R₃ and W₂,R₂₃ and W₁, R₂₃ and W₂, R₄ and W₃, R₃ and R₄, R₂₄ and W₃, and R₂₄ and W₄are, for example, 5- or 6-membered saturated or unsaturated condensedcarbocycles. These condensed rings can have substituents at theirarbitrary positions. The same groups as the groups substitutable to thealiphatic groups described above can be exampled for the substituentsfor the carbocycles.

[0087] The methylene groups represented by L₁ to L₉ in the generalformulae (11) and (12) represent each independently substituted orunsubstituted methylene. Concrete examples of the groups to besubstitutent of the methylene groups include substituted orunsubstituted lower alkyl, e.g., methyl, ethyl, isopropyl, benzyl andthe like; alkoxy, e.g., methoxy, ethoxy and the like; aryloxy, e.g.,phenoxy, naphthoxy and the like; aryl, e.g., phenyl, naphthyl, p-tolyl,o-carboxyphenyl and the like; —N(V₁ V₂); —SR; and heterocycles, e.g.,2-thienyl, 2-furyl, N,N′-bis(methoxyethyl)barbiturate and the lie.

[0088] R represents lower alkyl, aryl or a heterocycle as describedabove, V₁ and V₂ each represent substituted or unsubstituted, loweralkyl or aryl, and V₁ and V₂ can be bonded each other to form a 5- or6-membered nitrogen-containing heterocycle. Furthermore, the methylenegroup can bond with the adjacent methylene groups or with the methylenegroups beyond the next methylene groups thereof to form a 5- or6-membered ring.

[0089] When a group having cationic or anionic charges is substituted onthe compound represented by the general formulae (11) and (12),pair-ions are formed with the equivalent anionic or cationic ions sothat the charges in the molecules can be counterbalanced. For example,in connection to the ions required to counterbalance the chargesrepresented by X₁ in the molecules, concrete examples of the cationsinclude protons, organic ammonium ions (e.g., ions of each oftriethylammonium, triethanolammonium and the like), inorganic cations(e.g., cations of each of lithium, sodium, potassium and the like) andthe like, and concrete examples of the acid anions include halogenousions (e.g., chlorine ions, bromine ions, iodine ions and the like),p-toluenesulfonic acid ions, perchloric acid ions, boron tetrafluorideions, sulfuric acid ions, methylsulfuric acid ions, ethylsulfuric acidions, methanesulfonic acid ions, trifluoromethanesulfonic acid ions andthe like.

[0090] Now, the representative examples of the photosensitive colorantrepresented by the general formulae (11) and (12) will be given in thefollowing. However, it should be noted that the scope of thephotosensitive colorant according to this invention is not limited tothe examples given below.

[0091] The infrared-sensitizing colorants describe above can besynthesized according to the processes described in, for example, “Thechemistry of Heterocyclic Compounds”, by F. M. Harmer, vol. 18, “TheCyanine Dyes and Related Compound” (Published by A. Weissberger ed.Interscience Inc., New York, 1964), JP Tokukaihei-3-138638, 10-73900 and9-510022, U.S. Pat. No. 2,734,900, the specification of UK Patent No.774,779, JP Tokukai-2000-95958 and the specification of JPTokuganhei-11-58686.

[0092] In the present invention, the infrared-sensitizing colorant canbe used solely, but 2 or more thereof can be used in combination. Whenthe infrared-sensitizing colorant is used solely, and 2 or more thereofare used in combination, the colorants are contained in total in thesilver halide emulsion at a rate of 1×10⁻⁶ mol to 5×10⁻³ mol, preferably1×10⁻⁵ mol to 2.5×10⁻³ mol, and more preferably 4×10⁻⁵ mol to 1×10⁻³mol, relative to 1 mol of the silver halide. Besides, in the presentinvention, when the infrared-sensitizing colorants are used incombination, they can be contained in the silver halide emulsion atarbitrary combination ratios.

[0093] The photosensitive colorant according to this invention can bedispersed directly in the emulsion in accordance with the so-calledsolid dispersion method. Alternatively, the photosensitive colorant canbe dissolved in an appropriate solvent, e.g., methyl alcohol, ethylalcohol, n-propanol, methylcellosolve, acetone, water, pyridine or amixed solvent thereof, in advance and then added into the emulsion in aform of the solution. For dissolving the photosensitive colorant,supersonic can also be used. For the addition of the photosensitivecolorant, a method of dissolving the colorant in a volatile organicsolvent, followed by dispersing the solution in hydrophilic colloids andthen adding the dispersion into the emulsion, as described in U.S. Pat.No. 3,469,987, etc.; a method of dissolving the colorant with use of acompound to shift the colorant to long wavelength side and adding thesolution into the emulsion, as described in JP Tokukaisho-51-74624; amethod of dissolving the colorant in an acid substantially free of waterand adding the solution into the emulsion, as described in JPTokukaisho-50-80826, and the like can be preferably employed. Inaddition to the above methods, other methods described in U.S. Pat. Nos.2,912,343, 3,342,605, 2,996,287, 3,429,835, etc. can be employed foradding the photosensitive colorant according to this invention into theemulsion.

[0094] The photosensitive colorant according to this invention can beuniformly dispersed in the silver halide emulsion before the emulsion isapplied onto an appropriate support. In this concern, there is nolimitation for the timing of the addition of the colorant, and it can bedispersed at any stage.

[0095] When 2 or more of the photosensitive colorants according to thisinvention are used in combination, the colorants can be dispersedindependently into the silver halide emulsion or in a manner that thecolorants are combined in advance and then dispersed in the emulsionaccording to the procedures as described above. In addition to thephotosensitive colorants according to this invention, a colorant havingthe absorption at the visible light range, a colorant having no spectralsensitization activity by own, or a substance that substantially doesnot absorb visible light and exerting strong color sensitizationperformance can be contained in the emulsion. The useful sensitizingcolorants, the details of combinations of colorants with which thestrong color sensitization is exerted and substances exerting the strongcolor sensitization performance are described in, Research Disclosure,vol. 176, 17643 (published in 1978), page 23IV, section J; JPPublications Nos. sho-49-25500 and sho-43-4933; and JPTokukaisho-59-19032, 59-192242, H3-15049 and 62-123454.

[0096] Further, the above-described colorants and substances can beadded, instead of the silver halide emulsion, into the thermaldevelopment photosensitive layer containing a dispersion of silverhalide and an organic silver salt in which the silver halide and theorganic silver salt are mixed and are in contacting state with eachother. In this case, a spectral sensitizing colorant is properlydissolved in the coating solution for the thermal developmentphotosensitive layer so that it can be added to the photosensitivelayer. There is no limitation for the timing of the addition, and theaddition can be made at any stage. However, in general, it is convenientin view of the manufacturing to perform the addition during a periodbetween the stage following to the preparation of the organic silversalt dispersion containing the silver halide emulsion and the stagebefore performing the coating. In this case as well, the spectralsensitizing colorant can be added solely, or a plurality thereof can beadded in combination, or it can be added together with the substanceexerting the strong color sensitization performance. Further, thespectral sensitizing colorant can be added in the solid dispersionstate, that is, in which the particles of an insoluble colorant isdispersed in a solvent.

[0097] Now, the photothermographic imaging material according to thepresent invention will be described. The organic silver salt accordingto the present invention is a silver source capable of being reduced andis an organic acid that contains silver ion source capable of beingreduced. The organic acid used in the present invention includesaliphatic carboxylic acids, carbocyclic carboxylic acids, heterocycliccarboxylic acids and heterocyclic acids, however, it is preferable touse particularly an aliphatic carboxylic acid in a long chain (having 10to 30 carbon atoms, preferably 15 to 25 carbon atoms), a heterocycliccarboxylic acid including a nitrogen-containing heterocycle or the like.Further, it is also useful to use an organic silver salt complex ofwhich ligand having a total stability constant of 4.0 to 10.0 againstsilver ions.

[0098] An example of the above-described organic acid silver salt isdescribed in Nos. 17029 and 29963 of Research Disclosure (hereinafterreferred to RD). In particular, silver salts of fatty acids arepreferably used in this reference, and the particularly preferred aresilver behenate, silver arachidate and silver stearate.

[0099] The organic silver compound described above can be obtained bymixing an aqueous silver compound and a compound forming a complex withsilver. For this mixing, any of normal mixing method, reversible mixingmethod and simultaneous mixing method is preferably used. It is alsopossible to use the controlled double jet method as described in JPTokukaihei-9-127643A.

[0100] In the present invention, it is preferable that the organicsilver salt has an average particle size of 1 μm or less and ismonodispersed. The average particle size of the organic silver salt isdefined as the diameter of the particle converted into a spherical shapeof the organic silver salt, of which volume is equal to the volume ofany of the other shapes, when the particle of the organic silver salt isin any of spherical, rod-like or flat shape. The average particle sizeof the organic silver salt is preferably in a range of 0.01 to 0.8 μm,and is particularly preferable if it is in a range of 0.05 to 0.5 pm.The state of monodispersed is synonymous with that of silver halide willbe described later, and the monodispersed degree of the organic silversalt is preferably in a range of 1 to 30%. In the present invention, itis more preferable that the organic silver salt comprises monodispersedparticles having the average particle size of 1 μm or less, and imageswith higher density are obtainable by preparing the average size intothe above-defined range. Furthermore, it is preferable that the rate ofthe flat-shaped particles of the organic silver salt in number relativeto the whole particles of the organic silver is 60% or more. In thisinvention, the flat-shaped particle is defined as a particle of whichrate of the average particle size to the thickness, that is so-calledaspect ratio (hereinafter referred to as AR) represented by the equationdescribed below, is 3 or more.

AR=Average particle size (μm)/Thickness (μm)

[0101] It is preferable that the particles of organic silver salt asdescribed above are preliminary dispersed with a binder, a surfactant orthe like upon requirement and then dispersed/crushed by a mediadispersing apparatus or a high-pressure homogenizer. The dispersingapparatus usable in the preliminary dispersion includes, for example,ordinary stirrers of anchor type, propeller type and the like, stirrersof high-speed rotary centrifugal emission type (dissolver) and stirrersof high-speed rotary shearing type (homomixer). Further, examples of themedia dispersing apparatus include rotary mills, such as a ball mill, aplanet ball mill and a vibrating ball mill, a beads mill that is amedium stirring mill, atoriter, other basket mills and the like.Besides, as the high-pressure homogenizer, for examples, various typesincluding the type of impacting against plugs and the like, the type ofseparating liquid into plural portions and then impacting the portionswith each other at high speed, the type of passing through fine orificesand the like can be used.

[0102] In the apparatuses to be used for dispersing the organic silverparticles used in the present invention, it is preferable to use, forexample, ceramics, such as zirconia, alumina, silicon nitride and boronnitride, or diamond as a material for the members to which the organicsilver particles contact. Among the above materials, it is particularlypreferable to use zirconia.

[0103] The organic silver particles used in the present inventionpreferably contain Zr at a rate of 0.01 to 0.5 mg per 1 g of silver, andparticularly preferable to contain Zr at a rate of 0.01 to 0.3 mg. Whenthe above-described dispersion is carried out, it is greatly preferableto optimize the concentration of a binder, the preliminary dispersionmethod, the operational conditions for the dispersing apparatus, thefrequency of dispersing and so on for obtaining the organic silverparticles to be used in the present invention.

[0104] The smaller average particle size the photosensitive silverhalide according to the present invention has, the more preferable it isin view of inhibiting whitening after image forming and obtaining betterimage quality. The preferred average particle size is 0.1 μm or less,more preferably in a range of 0.01 to 0.1 μm, and particularlypreferably in a range of 0.02 to 0.08 μm. The particle size defined heredenotes the diameter of a circle that has an area equivalent to that ofthe individual particle image observed with an electron microscope(circle-equivalent diameter). Further, the silver halide is preferablymonodispersed. The monodispersed state used herein means that themonodispersed degree given from the equation described below is to be40% or less. The monodispersed degree of the particles is morepreferably 30% or less, and the particles of which monodispersed degreecomes to 20% or less are particularly preferable.

Monodispersed Degree=(Standard Deviation of Particle Size)/(Value ofAverage Particle Size)×100

[0105] Although there is no particular limitation to the shape of thephotosensitive silver halide particles, it is preferable that theproportion occupied by the Miller indices surface <100> is high. Thepreferred rate is 50% or more, the more preferred is 70% or more, andthe particularly preferred is 80% or more. The proportion of the Millerindices surface <100> can be measured according to the reference of T.Tani, J. Imaging Sci., 29, 165 (1985), where absorption dependency of<111> surface and <100> surface upon absorption of a sensitizingcolorant is utilized.

[0106] In the present invention, another preferable shape of thephotosensitive silver halide particle is plate-like. The plate-likeparticle defined herein means that the particle has an aspect ratio(r/h) of 3 or more when the square root of the projected area is r μmand the thickness in the vertical direction is h μm. In theabove-defined range of the aspect ratio, the preferred is in the rangeof 3 to 50. Further, the particle size of the plate-shaped particle ispreferably 0.1 μm or less, and more preferably in a range of 0.01 to0.08 μm. There is a description on such plate-shaped particles in U.S.Pat. Nos. 5,264,337, 5,314,798, 5,320,957, etc., and therefore, it ispossible to easily obtain purposive plate-shaped particles.

[0107] There is no particular limitation to the photosensitive halogencomposition, and it can be any of silver chloride, silverchloride/bromide, silver chloride/bromide/iodide, silver bromide, silveriodide/bromide and silver iodide. The emulsion used in the presentinvention can be prepared according to the processes described in suchpublications as, Chimie et Physique Photographique, by P. Glafkides(Published by Paul Montel Inc., 1967); Photographic Emulsion Chemistry,by G. F. Duffin (Published by The Focal Press, 1966); Making and CoatingPhotographic Emulsion, by V. L. Zelikman et al (Published by The FocalPress, 1964); and the like.

[0108] The photosensitive silver halide according to the presentinvention preferably contains metal ions of metals those belong to anyof the groups 6 to 11 of the periodic table. Among those metals, W, Fe,Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, Pt and Au are preferable.

[0109] These metal ions can be incorporated into the silver halide inthe form of a metal complex or a metal complex ion. The metal complex ora metal complex ion is preferably a six-coordinate metal complexrepresented by a general formula given below.

[ML₆]^(m)  General Formula

[0110] In the above formula, M is a transition metal selected from theelements belonging to the groups 6 to 11 of the periodic table, L is aligand, and m denotes an integer of 0, −1, −2, −3 and −4. Specificexamples of the ligand represented by L include, a ligand of each ofhalides (fluorides, chlorides, bromides and iodides), cyanides,cyanates, thiocyanates, selenocyanates, tellurocyanates, azides andaquos, and nitrosyls, thionitrosyls and the like. Among theabove-exemplified, the preferred is aquo, nitrosyl, thionitrosyl and thelike. When the aquo ligand exists, it is preferable that the aquo ligandoccupies one or two ligands. The ligands represented by L can be same ordifferent from one another.

[0111] M is preferably rhodium (Rh), ruthenium (Ru), rhenium (Re),iridium (Ir) and osmium (Os), and specific examples of the transitionmetal complex ion containing any of the above-exemplified elementsinclude [RhCl₆]³⁻, [RuCl₆]³⁻, [ReCl₆]³⁻, [RuBr₆]³⁻, [OsCl₆]³⁻,[IrCl₆]⁴⁻, [Ru(NO)Cl₅]²⁻, [RuBr₄(H₂O)]²⁻, [Ru(NO)(H₂O)Cl₄]⁻,[RhCl₅(H₂O)]2—, [Re(NO)Cl₅]2—, [Re(NO)(CN)₅]²⁻, [Re(NO)Cl(CN)₄]²⁻,[Rh(NO)₂Cl₄]⁻, [Rh(NO)(H₂O)Cl₄]⁻, [Fe(CN)₆]³⁻, [Rh(NS)Cl₅]²⁻,[Os(NO)Cl₅]²⁻, [Cr(NO)Cl₅]²⁻, [Re(NO)Cl₅]⁻, [Os(NS)Cl₄(TeCN)]²⁻,[Ru(NS)Cl₅]²⁻, [Re(NS)Cl₄(SeCN)]²⁻, [Os(NS)Cl(SCN)₄]²⁻, [Ir(NO)Cl₅]²⁻,[Ir(NS)Cl₅]²⁻, and the like.

[0112] The metal ion, metal complex or metal complex ion described abovecan be one kind or can be a combination of two or more metals of thesame or different kinds, respectively. Generally the content of themetal ion, metal complex and metal complex ion is suitably in a range of1×10⁻⁹ to 1×10⁻² mol, and preferably in a range of 1×10⁻⁸ to 1×10⁻⁴,relative to 1 mol of silver halide.

[0113] It is preferable that a compound that supplies any of theabove-described metals is added at the time of forming the silver halideparticles and incorporated into the particles of the silver halide.Although the compound can be added at an arbitrary stage prior to orafter the preparation of the silver halide particles, that is, formingcores, developing, physical aging and chemical sensitization, it isparticularly preferable to add the compound at the stage of formingcores, developing and physical aging, more preferably at the stage offorming cores and developing, and most preferably at the stage offorming cores.

[0114] A quantity of the compound can be divided into portions to addthe portions over several times. The compound can be distributeduniformly in the silver halide particles or incorporated so that thecompound forms a distribution pattern in the particles as described inJP Tokukaisho-63-29603A and Tokukaihei-2-306236A, 3-167545A, 4-76534A,6-110146A, 5-273683A and so on. It is preferable that the compound formsany distribution pattern in the silver halide particles. Each of themetallic compounds can be added in the form of solution in either wateror an appropriate solvent (e.g., alcohols, ethers, glycols, ketones,esters and amides). More specifically, the metallic compound can beadded in accordance with any of the following methods, for example, amethod of adding in advance an aqueous solution of a powdered metalliccompound or an aqueous solution in which a metallic compound, NaCl andKCl are dissolved together to a solution of aqueous silver salt or asolution of aqueous halide, that is under forming particles; a method ofadding the metallic compound as the third aqueous solution when a silversalt solution and a halide solution are simultaneously incorporated, toprepare the silver halide particles in a manner of simultaneousincorporation of the three solutions; a method to charge an aqueoussolution of a metallic compound in a required amount into a reactionvessel under forming the particles; and a method of adding anotherportion of silver halide particles having been doped with the ions orcomplex ions of a metal in advance at the time of preparing the silverhalide and dissolve them. Among those methods described above, it ispreferable to employ the method of adding an aqueous solution, in whichan aqueous solution of a powdered metallic compound or a metalliccompound is dissolved together with NaCl and KCl, to a solution of anaqueous halide.

[0115] When adding the metallic compound to the surfaces of theparticles, it is also possible to charge a required amount of themetallic compound solution into a reaction vessel just after forming theparticles, or on the way or after completion of the physical aging, orduring the chemical aging.

[0116] In the present invention, desalting of the photosensitive silverhalide particles following to forming the particles can be or can not berequired. However, when the desalting is applied, washing and desaltingcan be carried out according to a known method in the field, forexample, the noodle method, the flocculation method or the like.

[0117] It is preferable for the silver halide particles to be chemicallysensitized. The methods for chemically sensitizing the particles usablein the present invention include sulfur sensitization method, seleniumsensitization method, tellurium sensitization method and the like, whichare well known in the field. Besides, the noble metal sensitizationmethod using a gold, platinum, palladium, or iridium compound and thereduction sensitization method also can be used.

[0118] As the compounds suitably used for the above-described methods ofsulfur sensitization method, selenium sensitization method and telluriumsensitization method, compounds in the public domain can be used. Forexample, compounds disclosed in JP Tokukaihei-7-128768A can be used forsuch methods. As a tellurium sensitizing agent, for example,diacyltellurides, bis(oxycarbonyl)tellurides, bis(carbamoyl)tellurides,diacyltellurides, bis(oxycarbonyl)ditellurides,bis(carbamoyl)ditellurides, compounds each having P—Te bond(s),tellurocarboxylates, Te-organyltellurocarboxylic acid esters,di(poly)tellurides, tellurides, tellurols, telluroacetals,tellurosulfonatos, compounds each having P-Te bond(s), Te-containingheterocycles, tellurocarbonyl compounds, inorganic tellurium compounds,colloidal tellurium, and the like can be used.

[0119] As the compounds suitably used in the noble metal sensitizationmethod, for example, chloroauric acid, potassium chloroaurate, potassiumaurithiocyanate, gold sulfide, gold selenide, and compounds disclosed inU.S. Pat. No. 2,448,060 and UK Patent No. 618,061, etc. can be given.

[0120] As the compound used in the reduction sensitization method, forexample, in addition to ascorbic acid and thiourea dioxide, stannouschloride, aminoiminomethanesulfinic acid, hydrazine derivatives, boranecompounds, silane compounds, polyamine compounds and the like can beused. In addition, the reduction sensitization can be achieved byretaining pH of the solver halide emulsion at 7 and pAg thereof at 8.3or less and then carrying out the aging. Also, the reductionsensitization can be achieved by incorporating the single additionportion of solver ions under forming the particles.

[0121] It is preferable for the photothermographic imaging materialaccording to the present invention to contain a reducing agent.Generally-known reducing agents can be used for the photothermographicimaging material of the present invention. For example, phenols,polyphenols each including 2 or more phenol groups, naphthols,bisnaphthols, polyhydroxybenzenes each including 2 or more hydroxygroups, polyhydroxynaphthalenes each including 2 or more hydroxy groups,ascorbic acids, 3-pyrazolidones, pyrazoline-5-ones, pyrazolines,phenylenediamines, hydroxylamines, hydroquinone monoethers, hydroxamicacids, hydrazides, amidoximes, N-hydroxyureas can be given as examplesof the reducing agent. More specifically, the reducing agentsspecifically disclosed in U.S. Pat. Nos. 3,615,533, 3,679,426,3,672,904, 3,751,252, 3,782,949, 3,801,321, 3,794,488, 3,893,863,3,887,376, 3,770,448, 3,819,382, 3,773,512, 3,839,048, 3,887,378,4,009,039, 4,021,240, UK Patent No. 1,486,148, Belgium Patent No.786,086, JP Tokukaisho-50-36143A, 50-36110A, 50-116023A, 50-99719A,50-140113A, 51-51933A, 51-23721A and 52-84727A, and JP Sho-51-35851B canbe given. Any of the reducing agents in the public domain exemplifiedabove can be selected fitly to use for the present invention. In theselection of the reducing agent, it is the most efficient way topractically prepare the photothermographic imaging materials eachcontaining a respective reducing agent and directly assess itsphotographic performance to check propriety of the reducing agent.

[0122] Among the reducing agents exemplified above, when an aliphaticcarboxylic acid silver salt is used as an organic silver salt, preferredones include: polyphenols in each of those which two or more phenolgroups are connected by alkylene groups or sulfur atoms; in particular,polyphenols in each of those which two or more phenol groups each beingsubstituted with alkyl (e.g., methyl, ethyl, propyl, t-butyl, cyclohexy,etc.) or acyl (e.g., acetyl, propionyl, etc.) on at least one ofpositions adjacent to hydrogen-substituted position in the phenol groupare connected by alkylene groups or sulfur atoms; polyphenol compoundsdisclosed in U.S. Pat. Nos. 3,589,903 and 4,021,249, UK Patent No.1,486,148, JP Tokukaisho-51-51933, 50-36110, 50-116023, 52-84727 and JPSho-51-35727B, that is, for example,1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane,1,2-bis(2-hydroxy-3-t-butyl-5-methylphenyl)methane,1,1-bis(2-hydroxy-3,5-di-t-butylphenyl)methane,(2-hydroxy-3-t-butyl-5-methylphenyl)-(2-hydroxy-5-methylphenyl)methane,6,6′-benzylidene-bis(2,4-di-t-butylphenol),6,6′-benzylidene-bis(2-t-butyl-4-methylphenol),6,6′-benzylidene-bis(2,4-dimethylphenol),1,1-bis(2-hydroxy-3,5-dimethylphenyl)-2-methylpropane,1,1,5,5,-tetrakis(2-hydroxy-3,5-dimethylphenyl)-2,4-ethylpentane,2,2-bis(4-hydroxy-3,5-dimethylphenyl)propane,2,2-bis(4-hydroxy-3,5-di-t-butylphenyl)propane and the like;bisnaphthols disclosed in U.S. Pat. No. 3,672,904, for example,2,2′-dihydroxy-1,1′-binaphthyl,6,6′-dibromo-2,2′-dihydroxy-1,1′-binaphthyl,6,6′-dinitro-2,2′-dihydroxy-1, 1′-binaphthyl,bis(2-hydroxy-1-naphthyl)methane,4,4′-dimethoxy-1,1′-dihydroxy-2,2′-binaphthyl and the like;sulfonamidephenols or sulfonamidenaphthols as disclosed in U.S. Pat. No.3,801,321, that is, for example, 4-benzenesulfonamidephenol,2-benzenesulfonamidephenol, 2,6-dichloro-4-benzenesulfonamidephenol, and4-benzenesulfonamidenaphthol; polyphenol compounds disclosed in JPTokugan-2002-32225 and 2002-119143; and the like. Among the compoundsexemplified above, the particularly preferred are polyphenol compoundsdisclosed in JP Tokugan-2002-32225 and 2002-119143.

[0123] An appropriate quantity of the reducing agent used for thephotothermographic imaging material according to the present inventionvaries depending on the type of the organic silver salt to be used, thetype of the reducing agent, and the other additives. However, theappropriate quantity to be used is typically in a range of 0.05 to 10mol, preferably 0.1 to 3 mol, relative to 1 mol of the organic silversalt. Note that 2 or more of the reducing agents exemplified above canbe used in combination as far as the quantity thereof in total fallswithin the above-defined range. In the present invention, it ispreferable to add the reducing agent to the coating solution for thephotosensitive layer just before applying the coating solution in orderto minimize fluctuation in the photographic performance due to theeffect deriving from the stationary period of time of the coatingsolution for the photosensitive layer.

[0124] Now, the constitutional elements of the photothermographicimaging material according to the present invention except thecharacteristics having been explained above will be described below.

[0125] The photothermographic imaging material according to the presentinvention is formed by laminating an image forming layer containing theabove-explained organic silver salt, photosensitive silver halide and areducing agent and a protective layer in this order onto a support. Inaddition, upon requirement, an intermediate layer is further formedbetween the support and the image forming layer to thereby provide thephotothermographic imaging material in a preferable form.

[0126] Further, the photothermographic imaging material provided with abacking layer on the face opposing to the image forming layer forsecuring the feeding performance and preventing from blocking with theprotective layer can be suitably used. Note that each of those layerscan comprise a single layer or, 2 or more layers comprising the same ordifferent compositions.

[0127] In the present invention, a resin binder is preferably used forforming the respective layers described above. For such a resin binder,any of transparent or opaque resins for binder use having beenconventionally used can be appropriately selected and used. Examples ofsuch a resin binder include, poly(vinyl acetal) resins, such aspoly(vinyl formal), poly(vinyl acetoacetal) and poly(vinyl butylal);cellulose system resins, such as ethyl cellulose, hydroxyethyl celluloseand cellulose acetate butyrate; styrene resins, such as polystyrene,styrene-acrylonitrile copolymer and styrene-acrylonitrile-acryl rubbercopolymer; vinyl chloride resins, such as poly(vinyl chloride) andchlorinated polypropylene; polyesters, polyurethanes, polycarbonates,polyacrylates, epoxy resins, acryl resins, and the like. These resinsexemplified above can be used either alone or in combination of 2 ormore thereof.

[0128] Any of the binder resins can be used selectively upon requirementfor the protective layer, the intermediate layer, or the back coatlayer. The back coat layer is provided if it is necessary, unless theuse of the resin does not impair the object of the present invention.Note that an epoxy resin, an acryl monomer and the like, that arecurable with active energy rays, can be used as the binder resin forforming the layers. In the present invention, aqueous binder resins asexemplified below can also be preferably used.

[0129] As the preferable resin to be used, water-soluble polymers orwater-dispersible hydrophobic polymers (latexes) can be given. Examplesof such polymers include poly(vinylidene chloride), copolymer ofvinylidene chloride and acrylic acid, copolymer of vinylidene chlorideand itaconic acid, poly(sodium acrylate), poly(ethylene oxide),copolymer of acrylic amide and acrylate, copolymer of styrene and maleicanhydride, acrylonitrile-butadiene copolymer, copolymer of vinylchloride and vinyl acetate, copolymer of styrene and butadiene andacrylic acid, and the like. Although each of these polymers is in thestate of aqueous coating solution, it is dried after the coating wasmade and forms a uniform film of resin at the time when formation of thecoated film was completed. When any of such polymers is used, an organicsilver salt, silver halide, a reducing agent or the like is used as anaqueous dispersant and mixed with any of said latexes to prepare auniform dispersion, followed by coating of the dispersion, allowing toform the thermal development image forming layer. The particles of thelatex are fused during drying to form a uniform film. Further, it ispreferable to use a polymer having glass transition point is in a rangeof from −20 to 80° C., and particularly preferable from −5 to 60° C.This is because, a temperature required for the thermal developmentbecomes high if the glass transition point is higher than theabove-defined range, while fogging tends to occur, which causesdeterioration of the sensitivity and induce soft focus if the glasstransition point is lower than the above-defined range. As thewater-dispersible polymer, it is preferable to use the one in which theparticulates having the average particle size in a range of from 1 nm toseveral μm are dispersed. Water-dispersible hydrophobic polymer iscalled latex. Among latexes having been used widely for aqueouscoatings, it is preferable to use latex that can improve resistance towater. The quantity of the latex to be used as a binder for improvingresistance to water is determined in consideration of the coatingproperty. However, in view of the moisture-resistant property, it isbelieved that the greater quantity gives better result in the moistureresistance. Thus, the rate of the latex to the whole mass of the binderis preferably in a range of from 50 to 100%, and particularly preferablefrom 80 to 100%.

[0130] In the present invention, the solid content of any of the binderresins is preferably 0.25 to 10 times of the quantity of silver to becoated. For example, when the coated quantity of silver is 2.0 g/m², thequantity of the polymer to be coated is preferably in a range of from0.5 to 20 g/m². More preferably, the solid content of the binder resinis in a range of from 0.5 to 7 times of the coated quantity of silver.In this case, for example, when the coated quantity of silver is 2.0g/m², the solid content of the polymer is 1.0 to 14 g/m². On the otherhand, it becomes useless because silver tone greatly deteriorates whenthe quantity of the binder resin is less than 2.5 times of the coatedquantity of silver, while it becomes useless because of soft focus whenthe quantity of the binder resin is greater than 10 times of the coatedquantity of silver.

[0131] In addition, various additives, such as an antifoggant, a toner,a sensitizing colorant, and a substance inducing supersensitization(also designated as a supersensitization agent), can be added uponnecessity to the image forming layer according to the present inventionin addition to the above-described essential components and the binderresin.

[0132] In the present invention, for example, compounds disclosed inU.S. Pat. Nos. 3,874,946 and 4,756,999, heterocyclic compounds eachincluding one or more substituents represented by a formula—C(X¹)(X²)(X³), (wherein X¹ and X² each represent a halogen atom, and X³represents hydrogen or a halogen atom), compounds disclosed in JPTokukaihei-9-288328 and 9-90550, U.S. Pat. No. 5,028,523, EuropeanPatent Nos. 600,587, 605,981 and 631,176, etc. can be used as anantifoggant upon necessity.

[0133] Examples of the toner that is added for improving silver toneafter development include, imides (e.g., phthalimide); cyclic imides,pyrazoline-5-ones, and quinazoline (e.g., succinimide,3-phenyl-2-pyrazoline-5-one, 1-phenylurazole, quinazoline and2,4-thiazolidinedione); naphthalimides (e.g.,N-hydroxy-1,8-naphthalimide); cobalt complexes (e.g., hexaminetrifluoroacetate of cobalt), mercaptans (e.g.,3-mercapto-1,2,4-triazole); N-(aminomethyl)aryldicarboxyimides (e.g.,N-(dimethylaminomethyl)phthalimide); blocked pyrazoles, combinations ofisothiuronium derivatives and a certain kind of photobleaching agent(e.g., a combination ofN,N′-hexamethylene(l-carbamoyl-3,5-dimethylpyrazole),1,8-(3,6-dioxaoctane)bis(isothiuroniumtrifluoroacetate) and2-(tribromomethylsulfonyl)benzothiazole); merocyanine dyes (e.g.,3-ethyl-5-((3-ethyl-2-benzothiazolinylidene(benzothiazolinylidene))-l-methylethylidyne)-2-thio-2,4-oxazolidinedione);phthalazinone, phthalazinone derivatives or metal salts thereof (e.g.,4-(1-naphthyl)phthalazinone, 6-chlorophthalazinone,5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione);combinations of phthalazinone and sulfinic acid derivatives (e.g.,6-chlorophthalazinone+sodium benzenesulfinate, or8-methylphthalazinone+sodium p-trisulfonate); combinations ofphthalazine and phthalic acid; combinations of phthalazine (includingadducts of phthalazine), maleic anhydride and at least one selected froma group consisting of phthalic acid, 2,3-naphthalenedicarboxylic acid,or o-phenylenic acid derivatives and anhydrides thereof (e.g., phthalicacid, 4-methylphthalic acid, 4-nitrophthalic acid andtetrachlorophthalic anhydride); quinazolinediones, benzoxazine,nartoxazine derivatives; benzoxazine-2,4-diones (e.g.,1,3-benzoxazine-2,4-dione); pyrimidines and asymmetric-triazines (e.g.,2,4-dihydroxypyrimidine), and tetraazapentalene derivatives (e.g.,3,6-dimercapto-1,4-diphenyl-1H,4H-2,3a,5, 6a-tetraazapentalene) . Amongthe examples recited above, the preferred toners are phthalazone andphthalazine. Note that the toner in only a certain quantity range thatwill not inhibit the object of the present invention can be added to theprotective layer described later.

[0134] As the supersensitizing agent, compounds disclosed in RD No.17643, JP Hei-9-25500B, 43-4933B, JP Tokukaisho-59-19032A, and59-192242A and Tokukaihei-5-341432A, etc. can be selected to use uponnecessity. In the present invention, aromatic heterocyclic mercaptocompounds represented by the following general formula (M) and disulfidecompounds represented by a general formula (Ma) substantially generatingthe above-described mercapto compounds can be used as thesupersensitizing agent.

Ar—SM  General Formula (M)

Ar—S—S—Ar  General Formula (Ma)

[0135] In the general formula (M), M represents hydrogen or an alkalimetal atom, and Ar presents an aromatic heterocycle or a condensedaromatic heterocycle, having one or more atoms selected from a groupconsisting of nitrogen, sulfur, oxygen, selenium and tellurium. Thearomatic heterocycle is preferably benzimidazole, naphthoimidazole,benzothiazole, naphthothiazole, benzoxazole, naphthoxazole,benzoselenazole, benzotellurazole, imidazole, oxazole, pyrazole,triazole, triazine, pyrimidine, pyridazine, pyrazine, pyridine, purine,quinoline or quinazoline. In the general formula (Ma), Ar is synonymouswith the general formula (M).

[0136] The aromatic heterocycle described above can include substituentsselected from a group consisting of, for example, halogen atoms (e.g.,Cl, Br and I), hydroxy, amino, carboxyl, alkyl (e.g., alkyl groups eachcontaining one or more carbon atoms, and preferably 1 to 4 carbon atoms)and alkoxy (e.g., alkoxy groups each containing one or more carbonatoms, and preferably 1 to 4 carbon atoms).

[0137] It is preferable for the supersensitizing agent used in thepresent invention to be used in the emulsion layer containing particlesof an organic silver salt and silver halide in a quantity range of from0.001 to 1.0 mol per 1 mol of silver, and particularly preferable in therange of from 0.01 to 0.5 mol per 1 mol of silver.

[0138] In the image recording layer according to the present invention,it is possible to render the layer to contain a large cyclic compoundcontaining hetero atoms. The large cyclic compound is preferably atleast 9- membered, more preferably 12- to 24-membered, and still furtherpreferably 15- to 21-membered cyclic compound, containing as the heteroatoms at least one species of atom selected from nitrogen, oxygen,sulfur and selenium.

[0139] The representative compounds of the large cyclic compounds arecrown ethers, those which are ones synthesized by Pederson in 1967 andvarious ones having been synthesized following to that special report.These compounds are described in C. J. Pederson, Journal of Americanchemical society vol. 86(2495), 7017-7036 (1967), G. W. Gokel, S. H.Korzeniowski, “Macrocyclic polyether synthesis”, Springer-Vergal (1982),etc.

[0140] Other than the additives described above, for example, asurfactant, an oxidant, a stabilizing agent, a plasticizer, aultraviolet radiation absorbent, and a coating auxiliary can be used inthe image forming layer according to the present invention. For theseadditives and the additives described previously, compounds described inRD Item 17029 (June, 1978, pages 9 to 15) are preferably used.

[0141] In the present invention, the image forming layer can comprise asingle layer or a plurality of layers consisting of the same ordifferent compositions. Note that the thickness of the image forminglayer is normally in a range of from 10 to 30 μm.

[0142] Now, the support and the protective layer, which are essentialcompositions for forming the layers of the photothermographic imagingmaterial according to the present invention, will be described below.

[0143] For the support used for the photothermographic imaging materialof the present invention, a resin film of, for example, acrylates,metacrylates, poly(ethylene terephthalate), poly(butyleneterephthalate), poly(ethylene naphthalate), polycarbonate, polyallylate,poly(vinyl chloride), polyethylene, polypropylene, polystyrene, nylon,aromatic polyamide, polyether ether ketone, polysulfone, polyethersulfone, polyimide, polyether imide, triacetyl cellulose, etc., a resinfilm comprising two or more of the resins exemplified above in the formof laminated layers, or the like can be used.

[0144] In the image recording method that will be described later, thesupport according to the present invention is developed by heat to formimages following to forming of the latent images. Therefore, the supporthaving been drawn into a film shape and thermally set is preferable inview of the dimension stability. Within a range by which theadvantageous effect of the present invention is not impaired, a filler,such as zinc oxide, barium sulfate and calcium carbonate, can be added.Note that the support is formed in a thickness in a range of from 10 to500 μm, and preferably from 25 to 250 μm.

[0145] As the protective layer to be used for the photothermographicimaging material according to the present invention, the binder resinsdescribed above in connection with the image forming layer can be usedby selecting any of them upon requirement.

[0146] As the additive to be incorporated to the protective layer, it ispreferable to contain a filler in order to prevent the images aftertheir thermal development from having damages and to secure the feedingperformance of the layer. When a filler is incorporated, the contentthereof in the whole composition forming the layer is preferably in arange of 0.05 to 30% by mass.

[0147] Furthermore, a lubricant and an antistatic agent can beincorporated into the protective layer for improving the lubrication andelectrification properties thereof. Examples of such a lubricantinclude, fatty acids, fatty acid esters, fatty acid amides,polyoxyethylene, polyoxypropylene, (denatured) silicon oils, (denatured)silicon resins, fluororesins, carbon fluoride, waxes, etc. Examples ofthe antistatic agent include, cationic surface-active agents, anionicsurface-active agents, nonionic surface-active agents, macromolecularantistatic agents, metal oxides and electro-conductive polymers,compounds listed in “11,290 Items of Commercialized Chemicals”, issuedby Kagaku Kogyo Nippo Co., Ltd., pages 875-876, compounds described inU.S. Pat. No. 5,244,773, columns 14 to 20, and the like. Further, withinthe range by which the object of the present invention is not impaired,various types of additives to be added into the image forming layer canbe incorporated into the protective layer also. The quantity of each ofthe additives to be incorporated into the protective layer is preferablyin a range of 0.01 to 20% by mass with respect to the whole compositionsforming the protective layer, and more preferably from 0.05 to 10% bymass.

[0148] In the present invention, the protective layer can be a singlelayer or a plurality of layers consisting of the same or differentcompositions. Note that the thickness of the protective layer isnormally in a range of from 1.0 to 5.0 μm.

[0149] In the present invention, in addition to the image forming layer,the support and the protective layer, an intermediate layer adapted toimprove film adhesion between the support and the image forming layerand a back coat layer for providing feeding and antistatic performancecan be formed. When these layers are formed, the thickness of theintermediate layer is normally in a range of 0.05 to 2.0 μm, and that ofthe backing layer is normally in a range of 0.1 to 10 μm.

[0150] Each of the coating solutions for the image forming layer, andthe protective layer, and further the intermediate and backing layers,the later two layers are formed upon necessity, can be prepared bydissolving or dispersing the components as described above,respectively, into a solvent.

[0151] As the solvent usable in the preparation described above, any ofsolvents each having a solubility parameter value in a range of 6.0 to15.0, which are set forth in a reference, “Solvent Pocket Book” editedby Organic Synthesis Chemistry Association, etc., can be used. Examplesof the solvents usable for the coating solutions for forming therespective layers according to the present invention include ketonessuch as, for example, acetone, isophoron, ethyl amyl ketone, methylethyl ketone, methyl isobutyl ketone and the like; alcohols such as, forexample, methyl alcohol, ethyl alcohol, n-propyl alcohol, isopropylalcohol, n-butyl alcohol, isobutyl alcohol, diacetone alcohol,cyclohexanol, benzyl alcohol and the like; glycols such as, for example,ethylene glycol, diethylene glycol, triethylene glycol, propyleneglycol, hexylene glycol and the like; ether alcohols such as, forexample, ethylene glycol monomethyl ether, diethylene glycol monoethylether and the like; ethers such as, for example, ethyl ether, dioxane,isopropyl ether and the like; esters such as, for example, ethylacetate, butyl acetate, amyl acetate, isopropyl acetate and the like;hydrocarbons such as, for example, n-pentane, n-hexane, n-heptane,cyclohexane, benzene, toluene, xylene and the like; and chlorides suchas, for example, methyl chloride, methylene chloride, chloroform,dichlorobenzene and the like. However, the usable solvents are notlimited to the examples recited above, and any solvents can be usedunless they impair the advantageous effect of the present invention.

[0152] The solvents exemplified above can be used either alone or incombination of several kinds thereof. Note that the residual amount ofthe solvent in the photothermographic imaging material can be controlledby appropriately setting the conditions such as temperature in the stepof drying following to the coating process. The residual amount of thesolvent is preferably in a range of from 5 to 1,000 mg/m², and morepreferably from 10 to 300 mg/m² in total.

[0153] When it is required to apply dispersing at the time of preparingthe coating solutions, a conventionally well-known dispersing apparatuscan be selected from, for example, double roll mill, triple roll mill,ball mill, pebble mill, cobol mill, tron mill, sand mill, sand grinder,Sqegvari atolighter, high-speed impeller dispersing apparatus,high-speed stone mill, high-speed impact mill, disper, high-speed mixer,homogenizer, supersonic dispersing apparatus, open kneader, continuouskneader and the like, and appropriately used for the dispersion.

[0154] For applying the coating solutions prepared as described above, acoater station known in the earlier development can be selected from,for example, extruding coater of the extrusion system, reverse rollcoater, gravure roll coater, air doctor coater, blade coater, air knifecoater, squeeze coater, impregnation coater, bar coater, transfer rollcoater, kiss coater, cast coater, spray coater and the like, andappropriately used for the application. Among the coaters exemplifiedabove, it is preferable to use an extruding coater of the extrusionsystem or a roll coater such as reverse roll coater in order to preventunevenness in the thickness of the formed layer from occurring.

[0155] Besides, there is no particular limitation to the coater in casethe image forming layer will not be damaged by the coater. However, ifthere is a fear that the solvent used for the coating solution forforming the protective layer dissolves the image forming layer when theprotective layer is applied, among the coater stations exemplifiedabove, it is needed to use an extruding coater of the extrusion system,a gravure coater, a bar coater or the like. Note that, when acontacting-type coater, such as a gravure coater and a bar coater, isused, the rotating direction of the gravure coater or bar coater can beeither forward or reverse. If the rotating direction is forward, therotation can be effectuated either at uniform speed or at a speed with acertain circumferential speed difference.

[0156] When laminating the respective constitutional layers, coating anddrying can be repeated for each of the layers. Alternatively, it is alsoallowable to simultaneously coat the superimposed layers by employingthe wet-on-wet system and then dry the layers. In this case, the coatingcan be achieved by using, for example, any of reverse roll coater,gravure roll coater, air doctor coater, blade coater, air knife coater,squeeze coater, impregnation coater, bar coater, transfer roll coater,kiss coater, cast coater, spray coater and the like, and extrudingcoater of the extrusion system in combination. In the coating ofsuperimposed layers by the wet-on-wet system, adhesion between the upperand lower layers can be improved because the upper layer is coated whilethe lower layer is still remained in wet condition.

[0157] Furthermore, in the present invention, at least following toapplying the coating solution for the image forming layer, it ispreferable to set the temperature for drying the coated film at a rangeof 65 to 100° C. in order to efficiently achieve the object of thepresent invention. If the drying temperature is lower than 65° C., thereaction can be completed insufficiently, leading to cause fluctuationsin the sensitivity along with the lapse of time. Besides, if the dryingtemperature is higher than 100° C., it is unfavorable since fogging(coloring) can occur in the photothermographic imaging material itselfin the state right after the manufacture thereof. In addition, althoughit is not possible to flatly defined the drying period of time becauseit depends on the volume of blowing air at the time of drying, it ispreferable to dry the coated film within 2 to 30 minutes if it is undera normal condition.

[0158] Besides, with respect to the drying temperature, the coated filmcan be dried just after the coating at the temperature in theabove-defined range, or the coated film can be dried at a temperaturelower than 65° C. in the initial stage and then at the above-definedrange in view of the object preventing Marangoni effect caused by thecoating solution during drying and the unevenness (orange peel-likesurface texture) of the film caused by the initial drying in thevicinity of the surface due to dried warm blowing air from occurring.

[0159] As described above, with the photothermographic imaging materialand the suitable process for manufacturing the same according to thepresent invention, the object of the present invention can be achieved.Furthermore, by optimizing the image forming method, it becomes possibleto obtain clear images with no interference fringes.

[0160] Now, the image forming method suitable for the photothermographicimaging material according to the present invention will be described indetail.

[0161] The image forming methods usable in this invention are classifiedinto three major aspects based on the angle given by a surface to beexposed and the direction of laser beams, the wavelength of the laserbeams, and the number of the laser beams to be used. Each of theclassified aspects can come into effect solely, or two or more of theaspects can be combined to achieve the image forming method. Byconstituting the method in such a way, it becomes possible to obtainclear images with no interference fringes.

[0162] In this invention, the suitable aspect of the image formingmethod is to form images by scanning exposure using laser beams whichgive an angle that never be substantially vertical with respect to thesurface of the photothermographic imaging material to be exposed. It isunderstood that, since light pass difference reaching the image forminglayer is increased by forcing the incident angle to be out of thevertical direction even when reflection light is supposed to begenerated at the interface of the layers, scattering in the light passand attenuation of the laser beams occurs to thereby cause lessoccurrence of the interference fringes. Note that the wording of “neverbe substantially vertical” means that the angle closest to the verticaldirection during laser scanning is preferably in a range of from 55° to88°, and more preferably from 60° to 86°, and still more preferably from65° to 84°.

[0163] In addition, a further suitable aspect of the image formingmethod according to the present invention is to form images by scanningexposure using longitudinal multi-laser of which exposure wavelength isnot single. By scanning with such longitudinal multi-laser beams ofwhich wavelength having a certain width, the occurrence of theinterference fringes becomes less comparing to scanning laser beams ofthe longitudinal single mode. Note that the wording of “longitudinalmulti” used here means that the exposure wavelength is not single.Normally, the distribution of the exposure wavelengths is required to be5 nm or more, and preferably 10 nm or more. Although there is noparticular limitation to the upper limit of the exposure wavelengthdistribution, it is normally 60 nm more or less.

[0164] In the image recording method described above, any ofgenerally-known lasers including solid lasers, such as ruby laser, YAGlaser, and glass laser; gas lasers, such as He—Ne laser, Ar ion laser,Kr ion laser, CO₂ laser, Co laser, He—Cd laser, N₂ laser and excimerlaser; semiconductor lasers, such as InGaP laser, AlGaAs laser, GaAsPlaser, InGaAs laser, InAsP laser, CdSnP₂ laser and GaSb laser; chemicallasers; pigment lasers; and the like can be appropriately selected touse for a desired application. However, the image forming method ischaracterized in that the semiconductor laser having a wavelength in arange of 600 to 1,200 nm is preferably used among the above-exemplifiedlasers in view of the maintenance and the size of the light source.

[0165] Besides, with respect to the laser used by a laser imager and alaser image setter, the beam spot diameters on the exposing surface ofthe photothermographic imaging material when scanning is applied to saidphotothermographic imaging material are generally in a range of 5 to 75μm for that of the short axis and in a range of 5 to 100 μm for that oflong axis. The laser beam scanning speed can be fixed at an optimumvalue for each photothermographic imaging material according to thesensitivity at a laser oscillation wavelength inherent to thephotothermographic imaging material and laser power.

[0166] Next, the photothermographic imaging material of the invention isfurther explained.

[0167] The photothermographic imaging material of the inventioncomprises a photosensitive silver halide and silver salt of aliphaticcarboxylate, wherein a photosensitive emulsion is prepared in that thephotosensitive silver halide is not present in a synthesis ofnon-photosensitive aliphatic carboxylate, and the photosensitive silverhalide is mixed after completion of the synthesis.

[0168] In the following, the photosensitive silver halide, an organicfatty acid silver salt, a binder, a crosslinking agent and variousadditives, the coating technique, and condition for light exposure anddevelopment, all of those which are used for the photothermographicimaging material according to this invention, will be described in turn.

[0169] (Photosensitive Silver Halide)

[0170] The photosensitive silver halide functions as a light sensor, andit is therefore preferable that the particle size of the photosensitivesilver halide is less in the dimension in order to diminish thewhitening after image formation and to form images with good imagequality. The average particle size of the silver halide is less than0.08 μm, preferably in a range of 0.01 to 0.08 μm, and particularlypreferable in a range of 0.02 to 0.06 μm. It is preferable that thecontent of the particles having the smaller particle size is 70% orhigher. On the other hand, in view of the sensitivity and the toneadjustment, the particles have preferably somewhat larger particle size.Therefore, the average particle size of the silver halide is preferablyless than 0.1 μm, more preferably in a range of 0.04 to 0.1 μm, and themost preferably in a range of 0.05 to 0.08 μm. The content of theparticles having the larger particle size is preferably not higher than30%.

[0171] There is no particular limitation for the shape of the particlesof the photosensitive silver halide, and the particles can take any formof normal crystal forms, such as cubical and octahedral, and abnormalcrystal forms, such as spherical, virgate, and plate-like. In addition,there is no particular limitation for the source of the silver halide,and any of silver chloride, silver chloride/bromide, silverchloride/iodide/bromide, silver bromide, silver iodide/bromide, andsilver iodide can be used.

[0172] The amount of the photosensitive silver halide to be used as asensing material is preferably in a range of 2 to 8%, and morepreferably 3 to 6% in terms of the silver rate relative to the amount ofthe nonphotosensitive aliphatic silver carboxylate that will bedescribed later.

[0173] It is preferable that the photosensitive silver halide accordingto this invention contains metal ions of metals those which belong tothe groups of 6 to 11 of the periodic law table of the elements in thehalf portion at the surface side of the volume of the particles. As themetals, the prefered are W, Fe, Co, Ni, Cu, Ru, Rh, Pd, Re, Os, Ir, andPt, and in particular preferred are Fe, Co, Ru, Rh, Re, Os and Ir. It ispreferable that ions of at least one of the above-enumerated elementsare contained in the portion of the surface side from the three fifthportion of the volume of the silver halide particles, and morepreferable that ions of the metals of the equivalent mol are containedin the portion of the surface side from three fourth portion of thevolume of the silver halide particles.

[0174] The ions of the metals can be introduced into the silver halidein the form of metal complexes or metal complex ions. As the metalcomplex or metal complex ions, a six-coordination complex represented bythe following general formula is preferred.

[ML₆]^(m) General  general formula

[0175] In the formula shown above, M represents a transition elementselected from the elements belonging to the groups 6 to 11 of theperiodic law table, L represents a ligand, and m is 0, 2, 3 or 4.Concrete examples of the ligand represented by L include ligands ofhalides, (e.g., fluorides, chlorides, bromides and iodides), cyanides,cyanates, selenocyanatos, tellurocyanatos, azides and aquos, andnitrosyl, thionitrosyls and the like. The preferred are acquo ligand,nitrosyl, thionitrosyl, etc. When the aquo presents, it is preferablethat it occupies one or two ligands. L can be same or different from oneanother.

[0176] Preferred concrete examples of M include rhodium (Rh), ruthenium(Ru), rhenium (Re), iridium (Ir) and osmium (s).

[0177] The metal ions, metal complexes and metal complex ions to be usedcan be one type, or those of 2 or more of the same metal or differentmetals can be used in combination. The contents of those metal ions,metal complexes and metal complex ions are appropriately in a range of1×10⁻⁹ mol to 1×10⁻² mol relative to 1 mol of the silver halide ingeneral, and preferably in a range of 1×10⁻⁸ mol to 1×10⁻⁴ mol.

[0178] The compounds supplying the above-described metals are preferablyadded during the preparation of the silver halide particles so that thecompound is incorporated in the silver halide particles. The addition ofthe compounds can be carried out at any stages during the preparation ofthe silver halide particles, that is, before or after the seedformation, the growth and physical aging of the particles, and theapplication of chemical sensitization. However, it is preferable to addthe compounds at the stage of the seed formation, the growth or thephysical aging, and more preferable at the stage of the seed formationor the growth, and most preferably at the stage of the seed formation.

[0179] The addition of the compound can be performed by dividing thecompound into several portions to incorporate each portion into thesilver halide particles over several times, or can be performed so as toform a given distribution of the compound in the particles in accordancewith methods described in JP Tokukaisho-63-29603, andTokukaihei-2-306236, -3-167545, -4-76534, -6-110146 and -5-273683, etc.The method of forming a distribution of the compounds in the particlesis preferred.

[0180] The compounds supplying the metals can be added following todissolving the compound in water or an appropriate organic solvent,e.g., alcohols, ethers, glycols, ketones, esters, and amides.Alternatively, the compound can be added according to, for example, amethod to add the aqueous solution of the powdered metal compound or thesolution in which the metal compound, sodium chloride and potassiumchloride are dissolved in together into the aqueous solution of silversalt or the aqueous halide solution during formation of the particles; amethod to add the metal compound in a form of the third aqueous solutioninto the silver salt solution and the halide solution when they aremixed at the same time to prepare the silver halide particle in a mannerof simultaneous mixing of three solutions; a method to charge a requiredquantity of the aqueous solution of the metal compound into a reactorduring formation of the particles; or a method to add the other silverhalide particles having been doped in advance with metal ions or metalcomplex to dissolve the metal compound during the preparation of thesilver halide. The particularly preferred is the method to add thesolution, in which the aqueous solution of the powdered metal compoundor the metal compound, sodium chloride, and potassium chloride aredissolved in together, into the aqueous halide solution.

[0181] Alternatively, when the metal compound is added onto the surfaceof the particles, a required quantity of metal compound in an aqueoussolution can be charged into the reactor just after the particlesformation, or during or after the end of the physical aging, or at thetime of the chemical aging.

[0182] The photosensitive silver halide particles need to be or need notto be desalted after the formation of particles. When they are desalted,the desalting can be performed by washing according to any of knownmethods in the field including the noodle method, the flocculationmethod and so on.

[0183] As the methods for preparing the silver halide emulsioncontaining the photosensitive silver halide particles according to thisinvention, the methods described in “Chimie et Physique Photographique”,by P. Glafkides (published by Paul Montel Corp., 1967); “PhotographicEmulsion Chemistry”, by G. F. Duffin (published by The Focal Press,1966); and “Making and Coating Photographic Emulsion”, by V. L. Zelikmanet al (published by The Focal Press, 1964) are given. The silver halideemulsion used for the present invention can be prepared according to anyof these methods. That is, the silver halide emulsion can be prepared byany of the acidic method, the neutral method, the ammonia method and thelike, and for reacting a soluble silver salt and a soluble halogenoussalt, any of the one side mixing method, the simultaneous mixing methodand the combination thereof can be employed.

[0184] As the representative example, the silver halide emulsion isprepared by mixing an aqueous solution of a silver salt and an aqueoussolution of a halide in a protective colloid solution (a hydrophiliccolloids, such as gelatin, is used) that will be the reaction motherliquor, followed by the seed formation and crystal growth. However, thedouble jet method is generally used as the method for adding a halidesolution and an aqueous silver salt solution. Further, among the doublejet method, the control double jet method, that mixes each of thecomponents while controlling pAg and pH to perform the seed formationand the crystal growth is the representative method. Further, the doublejet method includes various variations, for example, a method to performthe addition through two steps, that is, the first step to prepare theseed particles (the seed formation), followed by the second step toperform the growth of the particles under the same conditions or thealternative conditions. In short, it is well-known in the field tocontrol the crystal habit and the size of the crystals in various waysfollowing to fixing the conditions for mixing an aqueous solution of asilver salt and an aqueous solution of a halide in the mixing step inthe aqueous protective colloid solution. Following to the mixing step, adesalting step for removing excess salts from the prepared emulsion iscarried out. As the desalting process, the flocculation method that addsa flocculant to the prepared silver halide emulsion to flocculate thesilver halide particles together with gelatin functioning as theprotective colloids to separate the silver halide particles from thesupernatant containing the salts. In the desalting process, thesupernatant is removed by decantation operation, and dissolution,flocculation, and decantation operations are repeated in order to removeexcess salts contained in the gelatin precipitation containing thesilver halide particles having been flocculated and precipitated.Besides, it is well-known to remove soluble salts according to theultrafiltration. The ultrafiltration is a method to remove the undesiredsalts with low molecular weights with the use of a synthesizedultrafiltration film that does not allow particles having large particlesizes like the silver halide particles and gelatin to pass therethrough.

[0185] The content of the hydrophilic colloids contained in thephotosensitive silver halide particles used in this invention is 40 g orless relative to 1 mol of silver. The particularly preferred is 35 g orless.

[0186] Furthermore, in this invention, the amount of the hydrophiliccolloids is 6×10⁻⁶ g or more relative to 1 mol of the transitionelements contained in the silver halide particles, which is selectedfrom the elements belonging to the groups 6 to 11 of the periodic lawtable. Namely, the contents of the hydrophilic colloids and thetransition elements contained in the photosensitive silver halide areselected so as to satisfy the above-described conditions.

[0187] The photosensitive silver halide prepared according to thevarious methods as described above can be chemically sensitized with anyof, for example, sulfur-containing compounds, aurous compounds,platinous compounds, palladium compounds, silver compounds, tincompounds, chromic compounds, or the combinations thereof. The detailsof the process and procedures of the chemical sensitization aredescribed in, for example, U.S. Pat. No. 4,036,650, UK Patent No.1,518,850, JP Tokukaisho-51-22430, -51-78319, -51-81124, etc.Alternatively, at the time of converting the part of the organic silversalt into the photosensitive silver halide with use of the componentsfor forming the silver halide, an amide compound can be coexisted asdescribed in U.S. Pat. No. 3,980,482 in order to achieve thesensitization.

[0188] In the present invention, more preferred embodiments can beachieved by fixing the pH though the whole process of forming thephotosensitive silver halide in a range of 3 to 6, and preferably 4 to6. Note that, though the prepared photosensitive silver halide particlescan be desalted according to known desalting methods, such as the noodlemethod, the flocculation method, ultrafiltration and electrodialysis, itis possible to use the prepared photosensitive silver halide particlesfor the photothermographic imaging material without applying thedesalting.

[0189] (Organic Fatty Acid Silver Salt)

[0190] In this invention, organic silver salts are reducible silversource, and silver salts of organic acids and hetero organic acids,particularly aliphatic silver carboxylate with long chains (containing10 to 30, preferably 15 to 25 carbon atoms) and nitrogen-containingheterocyclic compounds, are preferable to use. The inorganic or organiccomplexes each of those which ligands having the total stabilityconstant to silver ions of 4.0 to 10.0 as described in “ResearchDisclosure” (hereinafter referred to as “RD”, occasionally), 17029 and29963 are also preferable to use. As examples of the preferred silversalt, the followings can be given.

[0191] Silver salts of Organic acids: Silver salts of gallic acid,oxalic acid, behenic acid, stearic acid, arachidic acid, palmitic acid,lauric acid. Carboxyalkylthiourea salt of silver: Silver salts of1-(3-carboxypropyl)thiourea, 1-(3-carboxypropyl)-3,3-dimethylthioureaand the like. Silver salts or complexes of polymer reaction products ofaldehyde and hydroxy-substituted aromatic carboxylic acid: Silver saltsor complexes of the reaction product of aldehydes (formaldehyde,acetoaldehyde, butylaldehyde, etc.) and hydroxy-substituted acids(salicylic acid, benzoic acid, 3,5-dihydroxybenzoic acid, etc.). Silversalts or complexes of thiones: Silver salts or complexes of3-(2-carboxyethyl)-4-hydroxymethyl-4-thiazoline-2-thione,3-carboxymethyl-4-thiazoline-2-thione and the like. Complexes or saltsof a nitrogen acid selected from imidazole, pyrazole, urazole,1,2,4-thiazole, 1H-tetrazole, 3-amino-5-benzylthio-1,2,4-triazole andbenzotriazole, and silver. Silver salts of saccharin,5-chlorosalicylaldoxime and the like, and silver salts of mercaptides.

[0192] Among the above, the preferred are silver behenate, silverarachidate and silver stearate. In this invention, 2 or more organicsilver salts are preferably mixed in view of improving developingperformance and forming silver images with high densities and highcontrasts. For example, it is preferable to mix a silver ion solutionwith a mixture of 2 or more organic acids to prepare the organic silversalts.

[0193] The organic silver salt compound is prepared by mixing an aqueoussilver compound and a compound of forming a complex with silver, and forthis purpose, the normal mixing method, the back mixing method, thesimultaneous mixing method, the control double jet method as describedin JP Tokukaihei-9-127643 and the like are preferably employed. Forexample, an alkali metal salt (e.g., sodium hydroxide, potassiumhydroxide, etc.) is added to an organic acid to prepare an organicalkali metal soap (e.g., sodium behenate, sodium arachidate, etc.),followed by mixing of the soap and silver nitrate or the like to preparethe crystals of an organic silver salt. During this reaction, the silverhalide particles can be contained in the mixture.

[0194] The organic silver salt according to this invention can be usedin various forms, however, the salt in plate-like shape is preferablyused. In particular, the organic silver salt in plate-shaped granuleshaving the aspect ratio of 3 or more and the average ratio of theaciform particles, when it is measured from the main plane direction, ina range of 1.1 to 10.0 is preferably used, since it is required tolessen the geometric anisotropy of two planes (main planes) having themaximum area and opposing to each other in parallel to thereby carry outthe charging in the photosensitive layer. Note that the more preferableratio of the aciform particles is more than 1.1 and less than 5.0.

[0195] In this invention, the plate-shaped organic silver salt particleshaving the aspect ratio of 3 or more means that the plate-shaped organicsilver salt particles occupy 50% or more of the total organic silversalt particles in number of the particles. Moreover, in the organicsilver salt according to this invention, the plate-shaped particles withthe aspect ratio of 3 or more preferably occupy 60% or more of the totalparticles in number of the particles, more preferably 70% or more (innumber of the particles), and particularly preferably 80% or more (innumber of the particles).

[0196] The aspect ratio (abbreviated as AR) is represented by thefollowing equation.

AR=Average Particle Size (μm)/Average Thickness (μm)

[0197] The aspect ratio of the plate-shaped organic silver saltparticles according to this invention is preferably 2.0, more preferablyin a range of 3 to 10. Because, the organic silver salt particles willtend to be compacted too much, if the aspect ratio is too low, and theother hand, the organic silver salt particles tend to be heavy andeasily dispersed in a state that they are adhered to each other,followed by easy occurrence of light scattering that accordingly lowersthe transparency property of the photothermographic imaging material, ifthe aspect ratio is too high. Therefore, it is considered that thepreferred ratio of the aspect ratio is the above-described range.

[0198] For determining the average particle size, the dispersed organicsilver salt is diluted, dispersed on the grid provided with a supportfilm made of carbon, and then photographed by a transmission electronmicroscope (manufactured by Nihon Densi: Type 2000FX) at a directmagnification of 5,000 for the measurements. The photographed negativesare taken as the digital images by a scanner for measuring the particlesizes (diameter corresponding to a circle) of more than 300 particleswith the use of an appropriate image processing software to calculatethe average particle size.

[0199] Besides, the average thickness is determined according to themethod using a transmission electron microscope (TEM) as will bedescribed hereunder.

[0200] Firstly, the photosensitive layer coated onto a support is stuckto an appropriate holder and then cut in a direction perpendicular tothe surface of the support with a diamond knife to prepare the ultrathinsection with a thickness of 0.1 to 0.2 μm. The ultrathin section isplaced on a mesh grid made of copper, then transferred onto a carbonfilm having been made hydrophilic by glow discharge, and the illuminatedfield images of the section are observed under TEM at a magnificationsof 5,000 to 40,000 while cooling the section at −130° C. or lower withliquid nitrogen. The images are recorded quickly on a film, an imagingplate or in a CCD camera. At this time, the parts of the sectioncontaining no breaks and sags are preferably selected as the field to beobserved.

[0201] As the carbon film, it is preferable to use a carbon filmsupported by an organic film, such as ultra-thin collodion and formbar,and more preferable to use a single carbon film prepared by forming acarbon film onto a substrate made of rock salt and then dissolving therock salt to remove it, or by removing the organic film with an organicsolvent or by ion etching. The preferred acceleration voltage of TEM isin a range of 80 to 400 kV, and particularly preferable in a range of 80to 200 kV.

[0202] The details of the observation techniques with use of an electronmicroscope and the sample preparation techniques can be referred to“Observation Techniques by Electron Microscope for Medicine and Biology”edited by Japanese Association of Electron Microscope, Kanto Branch”(published by Maruzen), “Preparation Technique of Biological Samples forElectron Microscope” edited by Japanese Association of ElectronMicroscope, Kanto Branch” (published by Maruzen), respectively.

[0203] The TEM images recorded onto an appropriate medium are preferablydecomposed to at least 1024×1024 pixels, and preferably to more than2048×2048 pixels, and subjected to the image processing on a computer.In order to perform the image processing, it is preferable to convertthe analog images recorded on the film by a scanner or the like andapply shading correction, contrast edge accent, etc. for the occasionthat has arisen. Then, the histogram is prepared, and the images aresubjected to the process of changing into two values to extract theportion corresponding to the organic silver. The thicknesses of morethan 300 of the extracted organic silver particles are manually measuredwith use of an appropriate software to give the average value.

[0204] Beside, the average value of the aciform ratio of theplate-shaped organic silver salt particles can be worked out accordingto the following method. First of all, the binder in the photosensitivelayer is swelled with an organic solvent that can dissolve the binder toexfoliate the photosensitive layer containing the plate-shaped organicsilver salt particles from the support. Then, supersonic washing withuse of the above-mentioned solvent, centrifugation and removal of thesupernatant are repeated 5 times for the photosensitive layer. Note thatall of the above-described operations are carried out under a safelight.

[0205] Then, the photosensitive layer is diluted with methyl ethylketone (MEK) so that the solid content of the organic silver is adjustedto 0.01%. The dilution is dispersed with supersonic and added bydropping onto a polyethylene terephthalate film having been madehydrophilic by glow discharge, followed by drying.

[0206] The film applied with the particles is preferably used for theobservations following to the application of bias deposition with Pt-Chaving. a thickness of 3 nm using electronic beams at an angle of 30degree with respect to the film surface in a vacuum depositionapparatus.

[0207] The prepared sample is observed as the fabricated electronicimage by a field emission scanning electron microscope (FE-SEM) at theacceleration voltage of 2 to 4 kV and at magnifications of 5000 to20000, and the image is stored in an appropriate recording medium.

[0208] It is convenient for the above-described operation to use adevice capable of AD-converting the image signal from the electronmicroscope main body and directly recording as the digital informationon a memory. However, analog images recorded on a Polaroid film or thelike are also usable by converting the analog images into the digitalimages with use of a scanner and applying shading correction, contrastedge accent, etc. for the occasion that has arisen.

[0209] In the procedure for the image processing described above, ahistogram is prepared at first, and the images are subjected to theprocess of changing into two values to extract the portion correspondingto the organic silver having the aspect ratio of 3 or more. Theunwillingly-flocculated particles are cut by appropriate algorithm ormanual operations and then subjected to a peripheral extraction. Then,the maximum length (MX LNG) and the minimum width (WIDTH) of eachparticle are measured for at least 1000 particles, respectively, andfollowed by working out of the aciform ratio for each particle accordingto the following equation. The maximum length of particle is definedhere as the maximum value of length when two points in the particle isconnected with a line. Besides, the minimum width of particle is definedhere as the minimum value of the distance between two parallel lineswhen the two parallel lines are drawn such that they are circumscribedto a particle.

Aciform Rate=(MX LNG)/(WIDTH)

[0210] Then, the average value of the aciform ratio for the wholemeasured particles is worked out. When the measurements are carried outaccording to the above-described procedure, it is preferable tothoroughly make correction of the length per one pixel (scalecorrection) and correction of the two-dimensional distortion of themeasuring system in advance with use of a standard sample. Uniform LatexParticles (DULP) commercialized by US Dow Chemical Inc. is preferablyused as the appropriate standard sample. As the standard sample,polystyrene particles having a variation coefficient of less 10% withrespect to a particle size of 0.1 to 0.3 μm is preferred to use.Specifically, a lot of polystyrene particles that secures a particlesize of 0.212 μm and the standard deviation of 0.0029 μm is available

[0211] The details of the image processing technique can be referred to“Applied Techniques for Image Processing, edited by Hiroshi Tanaka(published by Kogyo Chosakai)”. There is no particular limitation forthe image processing program and the image processing apparatus, as faras it is feasible to carry out the above-described operations. Luzex-IIImanufactured by Nireco Inc. can be given as an example.

[0212] There is no particular limitation for the method for forming theorganic silver salt particles having the shape as described above.However, it is advantageous to keep the mixing state at the time offorming the organic alkali metal salt soap and/or the mixing state atthe time of adding silver nitrate into the soap in good conditions andto optimize the mixing ratio of silver nitrate for the reaction with thesoap.

[0213] For the occasion that has arisen, it is preferable topreliminarily disperse the plate-shaped organic silver salt particlestogether with a binder, a surface-active agent, etc., and then dispersedand ground by a media disperser, a high-pressure type homogenizer or thelike. For the preliminary dispersing operation, general stirrers such asthe anchor-type and propeller-type stirrers, high-speed centrifugeemission type stirrer (Dissolver), and high-speed rotary shearing typestirrer (Homomixer) can be used.

[0214] As the media disperser, tumbling mills, such as ball mill, planetball mill and vibrating ball mill, and medium stirring mills, such asbeads mill, atoracter, and other basket mills can be used. As thehigh-pressure homogenizer, various types of homogenizers, for example, atype of causing the particles to impact against a plug or the like, atype of dividing liquid to a plurality of liquid portions and causingthose portions to impact to one another at a high speed, a type ofcausing particles to pass through fine orifices and the like can beused.

[0215] Examples of ceramics preferably used for the ceramic beads thatis used at performing the media dispersion include Al₂O₃, BaTiO₃,SrTiO₃, MgO, ZrO, BeO, Cr₂O₃, SiO₂, SiO₂—Al₂O₃, Cr₂O₃—MgO, MgO—CaO,MgO—C, MgO—Al₂O₃ (spinel), SiC, TiO₂, K₂O, Na₂O, BaO, PbO, B₂O₃, SrTiO₃(strontium titanate), BeAl₂O₄, Y₃Al₅O₁₂, ZrO₂—Y₂O₃ (cubic zirconia),3BeO—Al₂O₃—6SiO₂ (synthesized emerald), C (synthesized diamond),Si₂O—nH₂O, silicon nitride, yttrium-stabilized zirconia,zirconia-reinforced alumina, and the like. Among the above ceramics,yttrium-stabilized zirconia and zirconia-reinforced alumina (hereinafterthese ceramics containing zirconia are abbreviated as zirconia) areparticularly preferably used, in view of generation of less impurity dueto abrasion with the beads and the disperser at the dispersingoperation.

[0216] In the devices used at dispersing the plate-shaped organic silversalt particles, the material of the members to which the organic silversalt particles contact is preferably ceramics, such as zirconia,alumina, silicon nitride and boron nitride, or diamond, and it is mostpreferable to use zirconia.

[0217] When the above-described dispersion is carried out, theconcentration of the binder to add is preferably in a range of 0.1 to10% relative to the mass of the organic silver, and it is preferablethat the temperature of the solution does not exceed 45° C. during thewhole period of from the preliminary dispersion until the essentialdispersion. With respect to the conditions for the dispersion operation,in case a high-pressure homogenizer is used for dispersing, theoperation is carried out preferably under a pressure in a range of 29.42to 98.06 MPa and the operation is carried out preferably at least twice.Further, in case a media disperser is used for dispersing, the operationis preferably carried out at a circumferential speed of 6 to 13/sec.

[0218] It is also feasible to use zirconia as the parts of the beads andthe members and to incorporate zirconia into the dispersion emulsion atcarrying out the dispersion. This method is preferable and effective forimproving the photographic performance. Alternatively, it can be alsoeffective to add pieces of zirconia into the dispersion emulsionafterward or to add in advance at the time of the preliminarydispersion. There is no particular limitation for the method for theaddition. As an example, the zirconia solution with high concentrationscan be prepared by filling zirconia beads into a beads mill andcirculating MEK therein. This highly-concentrated zirconia solution canbe added at an appropriate stage and at an appropriate concentrationinto the dispersion emulsion.

[0219] In the photosensitive emulsion containing the photosensitivesilver halide and an organic silver salt, zirconium is preferablycontained at a rate of 0.01 to 0.5 mg per 1 g of silver, and morepreferably 0.01 to 0.3 mg per 1 g of silver. Further, zirconium ispreferably contained in the form of particulates having particle sizesof 0.02 μm or less.

[0220] Although there is no particular limitation for the conditions forpreparing the photosensitive emulsion having the characteristics asdescribed above, the following can be given as the preferred conditions,that is, to keep the mixing state at the time of forming the organicacid alkali metal salt soap and/or the mixing state at the time ofadding silver nitrate to the soap in good condition, to optimize therate of silver nitrate to be reacted with the soap, to use the mediadisperser or a high-pressure homogenizer at the time of dispersing andgrinding, to add the binder at a rate of 0.1 to 10% by mass relative tothe mass of the organic silver salt at the time of dispersing, tomaintain the temperature at 45° C. or lower through the period from thedrying until the essential dispersion, and to use a dissolver at thepreparation and stir the emulsion at a circumferential speed of 2.0m/sec or faster.

[0221] The projection area of the organic silver particles having aspecific projection area as described above and the ratio thereof to thewhole projection area are given by extracting the portions correspondingto the organic silver according to the method using TEM in the samemanner as described in the section describing about the determination ofthe average thickness of the plate-shaped particles having an aspectratio or 3 or more. At that time, the flocculated particles are treatedas one particle so that the areas of the respective particles are given.Similarly, the areas of the particles are determined with at least 1,000particles, preferably with 2,000 particles, and the given areas areclassified into three groups, that is, A: less than 0.026 μm², B: 0.025μm² or greater to less than 0.2 μm² and C: 0.2 μm² or greater. Thephotothermographic imaging material according to this inventionpreferably satisfy to contain the particles in such a manner that thetotal sum of the areas of the particles belonging to the.A groupoccupies 70% or more of the area measured for the whole particles, andthe total sum of the areas of the particles belonging to the C group is10% or less of the area measured for the whole particles.

[0222] When the above-described procedure is used to carry outmeasurements, it is preferred to sufficiently make correction of thelength per one pixel (scale correction) and correction of thetwo-dimensional distortion in the measuring system in advance with useof the standard sample.

[0223] The organic silver salt particles are preferably monodispersedparticles, and the preferred degree of monodispersion is 1 to 30%.Images with high densities can be given by making the particles into themonodispersed particles within this monodispersion range. The degree ofmonodispersion used here is defined by the following equation.

Degree of Monodispersion=(Standard Deviation of Particle Size)/(Averageof Particle Sizes)×100

[0224] The average particle size of the organic silver salt ispreferably in a range of 0.01 to 0.2 μm, and more preferably 0.02 to0.15 μm. The average particle size (a diameter corresponding to acircle) is meant as a diameter of a circle that has the equivalent areaas that of the image of an individual particle observed by an electronmicroscope.

[0225] In order to prevent the photothermographic imaging material fromloosing transparency, the total amount of the silver halide and theorganic silver salt is preferably in a range of 0.5 to 2.2 g per squaremeter as a value converted to the amount of silver. Images with hardtones can be given by adjusting the total amount within this range.

[0226] (Binder)

[0227] The binder suitable for the photothermographic imaging materialis either transparent or semi-transparent, and is generally colorless.Examples of the binder include media for forming natural polymersynthetic resins, polymers and copolymers, and other films, includinggelatin, gum arabic, poly(vinyl alcohol), hydroxyethyl cellulose,cellulose acetate, cellulose acetate butylate, poly(vinyl pyrrolidone),casein, starch, polyacrylic acid, polymethylmetacrylic acid, poly(vinylchloride), polymetacrylic acid, copoly(styrene-maleic anhydride),copoly(styrene-acrylonitrile), copoly(styrene-butadiene), polyvinylacetals (polyvinylformal, polyvinylbutylal, etc.), polyesters,polyurethanes, phenoxy resins, Poly(vinylidene chloride), polyepoxides,polycarbonates, poly(vinyl acetate), cellulose esters, polyamides. Theexampled above can be either hydrophilic or nonhydrophilic.

[0228] The material of the binder suitable for the photothermographicimaging material is any of polyvinylacetals, and the particularlypreferred for the binder is polyvinylbutylal. Besides, for thenonphotosensitive layers, such as an overcoating layer, and anundercoating layer, in particular, a protective layer and a backcoatinglayer, cellulose esters having higher softening temperatures,particularly polymers, such as triacetyl cellulose and cellulose acetatebutylate, are preferably used. Note that, for the occasion that hasarisen, any of the above-enumerated binders can be used in combination.

[0229] The polyvinylacetals given below can be used as the binder thatcan be suitably used in this invention. ACETOACETAL BUTYRAL ACETALACETYL HYDROXYL Tg VALUE POLYMER (mol %) (mol %) (mol %) (mol %) (mol %)(° C.) P-1 6 4 73.7 1.7 24.6 85 P-2 3 7 75.0 1.6 23.4 75 P-3 7 3 71.11.6 27.3 88 P-4 3 7 74.4 1.6 24.0 75 P-5 3 7 75.4 1.6 23.0 74

[0230] The binders shown in the table are used in an effective range sothat they can function as a binder, respectively. Such an effectiverange can be determined easily by persons who are skilled in the art.For example, as the guidance for the minimum amount of the organicsilver salt to be retained in the photosensitive layer, the ratio of thebinder and the organic silver salt is preferably in a range of 15:1 to1:2, and particularly preferably in a range of 8:1 to 1:1. That is, theamount of the binder in the photosensitive layer is preferably in arange of 1.5 to 6 g/m², and more preferably 1.7 to 5 g/m². If the amountis less than 1.5 g/m², the density in the unexposed portion will beincreased to a great extent, images with which cannot stand for thepractical use.

[0231] (Crosslinking Agent)

[0232] As the crosslinking agent used in this invention, variouscrosslinking agents having been conventionally used for ordinaryphotograph photosensitive material use, for example, aldehydes, epoxycompounds, ethylene imines, vinylsulfones, sulfonates, acryloyls,carbodiimides and silane compounds can be used. However, the preferredincludes isocyanate compounds, silane compounds and epoxy compounds, asdisclosed in JP Tokukaisho-50-96216. The details of these compounds aredescribed in JP Tokukai-2001-249428.

[0233] In this invention, a matting agent is preferably contained in thephotosensitive layer, and the matting agent is preferably provided inthe surface of the photographic material for preventing the thermallydeveloped images from being damaged. The matting agent is preferablycontained at a rate of 0.5 to 10% by mass relative to the mass of thewhole binder contained in the photosensitive layer side. The material ofthe matting agent used in this invention can be either an organiccompound or an inorganic compound. Examples of the inorganic mattingagent usable in this invention include silica disclosed in Swiss PatentNo. 330,158, glass powder disclosed in French Patent No. 1,296,995,alkaline metals or carbonates of cadmium, zinc, etc. disclosed in U.K.Patent No. 1,173,181. Examples of the organic matting agent usable inthis invention include starch disclosed in U.S. Pat. No. 2,322,037,starch derivatives disclosed in Belgian Patent No. 625,451 and U.K.Patent No. 981,198, poly(vinyl alcohol) disclosed in JP PublicationSho-44-3643, polystyrene or polymetacrylate disclosed in Swiss PatentNo. 330,158, polyacrylonitrile disclosed in U.S. Pat. No. 3,079,257,polycarbonate disclosed in U.S. Pat. No. 3,022,169, etc. and so on.

[0234] The shape of the matting agent can be either regular orirregular. However, the matting agent in a regular shape, particularlyin spherical shape is preferred. The size of the matting agent isrepresented by the diameter of a spherical particle which is convertedfrom the volume of the particles of the matting agent, and the particlesize of the matting agent used in this invention denotes the diameter ofthe spherical particle converted from the volume. The average particlesize of the matting agent used in this invention is preferably in arange of 0.5 to 10 μm, and more preferably 1.0 to 8.0 μm. The variationcoefficient of the particle size distribution of the matting agent ispreferably 50% or less, more preferably 40% or less, and particularlypreferably 30% or less. The variation coefficient of the particle sizedistribution used here is represented by an equation that is equivalentto the variation coefficient used for the silver salt particles. Thematting agent can be contained in an arbitrary structural layer, but thematting agent is added preferably into a structural layer other than thephotosensitive layer, and more preferably into the outermost layer fromthe support. As the method for adding the matting agent in thisinvention, a method to disperse the matting agent in a coating solutionin advance and then coat the solution, or a method to apply a coatingsolution at first and then spray the matting agent solution over thecoating solution before the coating solution having been dried, can beemployed. Furthermore, when a plurality of types of matting agents areadded, the both methods described above can be employ in combination.

[0235] It is preferred to add a color toning agent into thephotothermographic imaging material according to this invention.Examples of the suitable color toning agent are disclosed in RD17029,and the following are concrete examples enumerated therein.

[0236] Imides, e.g., phthalimide; cyclic imides, pyrazoline-5-ones andquinazolines, e.g., succinimide, 3-phenyl-2-pyrazoline-5-one,1-phenylurazole, quinazoline, 2,4-thiazolidinedione and the like;naphthalimides. e.g., N-hydroxy-1,8-naphthalimide and the like; cobaltcomplex, e.g., hexaminetrifluoroacetate of cobalt and the like;mercaptans, e.g., 3-mercapto-1,2,4-triazole and the like;N-(aminomethyl)aryldicarboxyimides, e.g.,N-(dimethylaminomethyl)phthalimide and the like; combinations of blockedpyrazoles, isothiuronium derivatives and a certain types ofphotobleaching agents, e.g., combinations ofN,N′-hexamethylene(1-carbamoyl-3,5-dimethylpyrazole,1,8-(3,6-dioxaoctane)bis(isothiuroniumtrifluoroacetate) and2-(tribromomethylsulfonyl)benzothiazole; merocyanine dyes, e.g.,3-ehtyl-5-((3-ethyl-2-benzothiazolinylidene(benzothiazolinylidine))-1-methylethylidene)-thio-2,4-oxazolidinedioneand the like; phthalazinone, phthalazinone derivatives and the metalsalts thereof, e.g., 4-(1-naphthyl)phthalazinone, 6-chlorophthalzinone,5,7-dimethyloxyphthalazinone, and 2,3-dihydro-1,4-phthalazinedione;combinations of phthalazinone and sulfinic acid derivatives, e.g.,6-chlorophthalazinone+sodium benzenesulfinate or8-methylphthalazinone+sodium p-trisulfonate; combinations of phthalazineand phthalic acid; combinations of phthalazine (including the additionproducts of phthalazine) and maleic anhydride, and at least one selectedfrom phthalic acid, 2,3-naphthalenedicarboxylic acid or o-phenylenicacid derivatives and the anhydride thereof (anhydrides of phthalic acid,4-methylphthalic acid, 4-nitrophthalic acid and tetrachlorophthalicacid); quinazolinediones, benzoxazine, nartoxazine derivatives;benzoxazine-2,4-diones, e.g., 1,3-benzoxazine-2,4-dione and the like;pyrimidines and asynmetric-triazines, e.g., 2,4-dihydroxypyrimidine andthe like; and tetraazapentalene derivatives, e.g.,3,6-dimercapto-1,4-diphenyl-1H,4H-2,3a,5,6a-tetraazapentalene and thelike. Among the above examples, the particularly preferred color toningagents is phthalazone or phthalazine.

[0237] (Layer Configuration)

[0238] The photothermographic imaging material according to thisinvention includes at least one layer of photosensitive layer on thesupport. The photosensitive layer can be formed solely on the support,however, it is preferable to form at least one nonphotosensitive layeronto the photosensitive layer. A filter layer can be formed on the sameside or the opposite side of the photosensitive layer, or the dyesaccording to this invention or known pigments can be directly containedin the photosensitive layer, in order to control the quantity of lightpassing through the photosensitive layer or wavelength distribution. Aplurality of photosensitive layers can be formed, and for the purpose ofcontrolling the color gradation, the photosensitive layers can compriselayers of different photosensitivities, for example,highly-photosensitive/low-photosensitive orlow-photosensitive/highly-photosensitive layers.

[0239] Various additives can be added into any of the photosensitivelayer, the nonphotosensitive layer or the other formed layers. Asurface-active agent, an oxidant, a stabilizer, a plasticizer, anultraviolet absorbent, an auxiliary for coating can be used for thephotographic materials according to this invention.

[0240] (Coating Technique)

[0241] The photothermographic imaging material according to thisinvention is preferably prepared by preparing a plurality of coatingsolutions in those which the materials for the above-describedstructural layers are dissolved in a solvent, respectively, applyingthose coating solution to form superimposed-layers at the same time, andthen heating the layers. The wording of “applying the plurality ofcoating solution to form superimposed-layers at the same time” meansthat, when coating solution for forming the respective structural layers(e.g., photosensitive layer, protective layer, etc.) are prepared andthen applied onto the support, the respective structural layer can beformed under the situation such that the coating solutions aresimultaneously applied to form superimposed-layers thereof andsimultaneously dried. The wording does not mean that the coatingsolutions are separately applied and dried in a repeated manner to formthe respective layers in turn. Namely, the upper layer is formed beforethe remaining content of the whole solvent in the lower layer hasdecreased to 70% by mass or less.

[0242] There is no particular limitation for the method for coating thecoating solutions to simultaneously form the respective structurallayers into the superimposed form, and any of the publicly-knownmethods, such as bar coater method, curtain coat method, dipping method,air knife method, hopper coating method and extrusion coating method,can be employed for this purpose. Among the above-exampled methods, themore preferred is the extrusion coating method of the pre-mensurationtype. In the extrusion coating, volatilization on the surface plane doesnot occur like it happens in the slide coating method. Therefore, theextrusion coating method suits for accurate coatings and coatings oforganic solvents. The coating methods to the side where thephotosensitive layer resides are described in the above, however, it canbe carried out in the same way when the backcoating layer is formedtogether with the undercoating layer.

[0243] (Conditions for Exposure)

[0244] For the exposure of the photothermographic imaging material, alight appropriate to the color sensitivity provided to the photographicmaterial is preferably used. For example, when the photographic materialis sensitive to infrared light, though it is applicable for any lightsource as far as the light source emits light in the infrared region, itis more preferred to use an infrared semiconductor laser (780 to 820 nm)because the laser has high power and transparent photographic materialscan be used.

[0245] The exposure is preferably performed by laser scanning exposure.However, various methods can be employed for the exposure. For example,the first preferred method is to use a laser scanning light exposureapparatus with which the angle between the plane to be exposed of thephotographic material and the scanning laser beams substantially neverbe at right angle. The wording of “substantially never be at rightangle” means that the closest angle to right angle during the laserscanning is preferably 55 to 88 degree, more preferably 60 to 86 degree,still more preferably 65 to 84 degree, and most preferably 70 to 82degree.

[0246] The diameter of the beam spot on the exposure plane when laserbeams are scanned on the photographic material is preferably 200 μm orless, and more preferably 100 μm or less. This is because that thesmaller spot diameter is preferred in view of a feasibility to reducethe offset angle of the laser incident angle from the right angle. Notethat the lower limit of the beam spot diameter is 10 μm. By performingthe laser scanning exposure as described above, the deterioration in theimage quality due to the reflection light, such as occurrence ofunevenness in the images like fringes by interference.

[0247] Further, as the second method, it is also preferable to carry outthe exposure with use of a laser scanning exposure apparatus that emitsscanning laser beams of the vertical multi-mode. With this method, thedeterioration in the images such as occurrence of unevenness in theimages like the interference fringes can be reduced comparing to laserbeams of the vertical single-mode. To convert to the verticalmulti-mode, methods to use jointed waves, to utilize returning light andto apply high-frequency superimposition can be preferably employed.

[0248] Note that the vertical multi-mode means that the wavelengthapplied for an exposure is not single, and the distribution of thewavelengths for an exposure is generally 5 nm or more, and preferably 10nm or more. There is no particular limitation for the upper limits ofthe exposure wavelength, however, it is 60 nm more or less in general.

[0249] Furthermore, as the third method, it is also preferred to use 2or more laser beams to perform scanning exposure to thereby form images.

[0250] Such an image recording method using a plurality of laser beamsis a technology having been used for the image printing included inlaser printers and digital copying machines, in which images are printedwith a plurality of lines for one time scanning for responding torequirements for high resolution and high-speed performance. This methodhas been known from the disclosure of JP Tokukaisho-60-166916, etc. Inthis method, laser beams irradiated from a light source unit aredeflection-scanned by a polygon mirror via an fθ lens or the like toform images onto a photosensitive body, and a laser scanning opticalapparatus based on this technology is in principle same as a laserimager and the like.

[0251] In the image forming onto a photosensitive body included in theimage printing of a laser printer or a digital copying machine, the nextlaser beam is shifted by one line from the position of images formed bythe previous laser beam to form images, since the apparatus is adaptedto print images with a plurality of line at one time scanning.Specifically, two laser beams are close to each other in the subscanningdirection at a distance in the order of 10 pm on the image formingsurface, the printing density is 400 dpi (dpi is meant as the number ofdots per one inch, that is 2.54 cm), and the subscanning direction pitchof the two laser beams is fixed at 63.5 μm. When the printing density is600 dpi, the pitch is fixed at 42.3 μm.

[0252] Unlike the method of shifting the lines on the photosensitivebody by one portion of resolution in the subscanning direction, it isalso preferred in this invention to alter the incident angles of two ormore laser beams so that the laser beams concentrate onto the samesurface to be exposed to form an image. In this method, the exposureenergy on the surface to be exposed in the normal operation whereprintings are performed with one laser beam (wavelength λ nm) is givenas E, and when n rays of laser beams used for an exposure have theequivalent wavelength (λ nm) and the equivalent exposure energy (En),the exposure energy is preferably fall with the range of0.9×E≦En×N≦1.l×E. By fixing the En in this range, the energy on thesurface to be exposed is retained, and the reflection of the respectivelaser beams to the image forming layer is reduced because the exposureenergy is low, and the interference fringes is prevented from occurring,accordingly.

[0253] Note that the wavelength of the plurality of laser beams is givenas λ in the above, different wavelengths can be used. When usingdifferent wavelengths, they preferably fall within the range of(λ−30)<λ1, λ2, . . . , λn≦(λ+30).

[0254] In the image forming methods of the first to third embodiments,commonly-known lasers can be used as the laser used for the scanningexposure. Examples of the laser include solid laser, such as ruby laser,YA laser and glass laser; gas laser, such as He—Ne laser, Ar ion laser,Kr ion laser, CO₂ laser, CO laser, He—Cd laser, N₂ laser and excimerlaser; semiconductor laser, such as InGaP laser, AlGaAs laser, GaAsPlaser, InGaAs laser, InAsP laser, CdSnP2 laser and GaSb laser; chemicallaser; pigment laser and the like, and any of these lasers can beselected appropriately corresponding to the usage. However, among theabove, semiconductor laser with a wavelength of 600 to 1200 nm ispreferably used in view of the maintenance and the dimension of thelight source. Besides, in the lasers used by a laser imager and a laserimage setter, the beam spot diameter on the exposure surface of aphotographic material when images are scanned onto a photo-thermalphotographic material is generally in a range of 5 to 75 μm for theshort axis and 5 to 100 μm for the long axis. The laser beam scanningspeed can be fixed to an optimal speed for every photographic materialin accordance with the sensitivity and laser power at the laseroscillation wavelength inherent to the photothermographic imagingmaterial.

[0255] (Conditions for Development)

[0256] The conditions for the development of the photothermographicimaging material vary depending on the hardware, apparatuses to be used.However, during developing operations, the photographic materials havingbeen exposed and formed images are typically heated at appropriatetemperatures. Latent images formed following to the exposure aredeveloped by heating the photographic materials for sufficient period oftime (developing process for 5 to 15 seconds is preferred in thisinvention) at moderately high temperatures (80 to 200° C., preferably100 to 150° C.).

[0257] If the heating temperature is lower than 80° C., images withsufficient image density cannot be formed in a short time. Besides, ifthe heating temperature is higher than 200° C., the binder could fuse,and high temperatures give damages not only to the images themselves butalso to the feeding performance such as the transfers to rollers and thedeveloping devices. Heating accelerates the oxidation and reductionreactions between the organic silver salt (functioning as an oxidant)and a reducing agent to form silver images. This reaction processproceeds without any supply including water, the processing solution andthe like from the exterior.

[0258] The devices, apparatuses used for the heating can be a typicalheat generating as a heat generator using a hot plate, an iron, a hotroller, carbon, white titanium or the like. More preferably, in casethat the photothermographic imaging material is provided with aprotective layer, it is preferable to render the heating to contact theside face of the protective layer in view of performing even heating,heating efficiency and handlings, and then to feed, heat and develop thephotosensitive material while causing the protective layer side tocontact the heat controller.

EXAMPLES

[0259] Hereinafter, the present invention is described in detail withreference to the examples. However, the present invention is not limitedto the following embodiments.

EXAMPLE 1 Preparation of Undercoated Support for Photograph

[0260] <Preparation of PET-undercoated Support for Photograph>

[0261] Corona discharge was applied to the both sides of a commerciallyavailable PET film having been biaxially oriented and thermally fixed,having a thickness of 175 μm and colored blue at an optical density of0.170 (measured by densitometer PDA-65 manufactured by Konica). Anundercoat coating solution a-1 will be described below was coated ontoone side of the film so that the coating after dried was formed in athickness of 0.8 μm, and the coating was then subjected to drying togive an undercoat layer A-1. Besides, an undercoat coating solution b-1was coated onto the opposite side of the film so that the coating afterdried was formed in a thickness of 0.8 μm, and the coating was subjectedto drying to give an undercoat layer B-1.

[0262] <<Undercoat Coating Solution a-1 >> Copolymer latex solution(solid content 30%) 270 g comprising: Butyl acrylate (30% by mass)t-Butyl acrylate (20% by mass) Styrene (25% by mass), and 2-Hydroxyethylacrylate (25% by mass) C-1  0.6 g Hexamethylene-1,6-bis(ethyleneurea) 0.8 g

[0263] Water is added to the whole components to adjust the whole volumeto 1 liter.

[0264] <<Undercoat Coating Solution b-1 >> Copolymer latex solution(solid content 30%) 270 g comprising: Butyl acrylate (40% by mass)Styrene (20% by mass) and Glycidyl acrylate (40% by mass) C-1  0.6 gHexamethylene-1,6-bis(ethyleneurea)  0.8 g

[0265] Water is added to the whole components to adjust the whole volumeto 1 liter.

[0266] Subsequently, corona discharge with a power of 8W/m²/min. wasapplied to the upper surfaces of the undercoat layers A-1 and B-1. Anupper undercoat coating solution a-2 described below was coated onto theundercoat layer A-1 so that the coating after dried was formed in athickness of 0.1 μm, thereby forming an upper undercoat layer A-2.Besides, an upper undercoat coating solution b-2 was coated onto theundercoat layer B-1 so that the coating after dried was formed in athickness of 0.8 μm, thereby forming an upper undercoat layer B-2 havingantistatic performance.

[0267] <<Upper Undercoat Coating Solution a-2>> Gelatin The mass to be0.4 g/m² C-1 0.2 g C-2 0.2 g C-3 0.1 g Silica particles (Average 0.1 gparticle size 3 μm)

[0268] Water is added to the whole components to adjust the whole volumeto 1 liter.

[0269] <<Upper Undercoat Coating Solution b-2>> C-4 60 g Latex solutioncomprising 80 g C-5 (solid content 20%) Ammonium sulfate 0.5 g  C-6 12 gPolyethylene glycol  6 g

[0270] (Mass Average Molecular Weight 600)

[0271] Water is added to the whole components to adjust the whole volumeto 1 liter.

[0272] <<Coating to Back Surface Side>>

[0273] To methyl ethyl ketone (MEK) in an amount of 830 g while beingstirred were added 84.2 g of cellulose acetate butylate (manufactured byEastman Chemical, Inc., CAB381-20) and 4.5 g of polyester resin(manufactured by Bostic, Inc., Vitel PE2200B) to prepare a solution.Then, to the solution was added 0.30 g of a dye 1, followed by additionsof 4.5 g of fluorinated surfactant (manufactured by Asahi Glass Co.,Ltd., Surflon KH40) having been dissolved in 43.2 g of methanol and 2.3g of fluorinated surfactant (manufactured by Dainippon Ink ChemicalsCo., Ltd., Megaface F120K), and further followed by thorough stirring todissolve the added active agents. As the last procedure, 75 g of silica(manufactured by W. R. Grace, Inc., Siloid 64X6000) having beendispersed by a dissolver-type homogenizer was added to methyl ethylketone at a concentration of 1% by mass, and the mixture was stirred togive a coating solution for the back surface side.

[0274] The back surface side coating solution prepared as describedabove was coated with using an extruding coater onto the upper undercoatlayer B-2 so that the coating after dried is formed in a thickness of3.5 μm, followed by drying. The drying was carried out for 5 min. at atemperature of 100° C. with dried blowing air of which exposuretemperature is 10° C.

[0275] <<Preparation of Photosensitive Silver Halide Emulsion>> A1Gelatin of phenylcarbamoyl form 88.3 g Compound (A) 10 ml (In 10%aqueous solution of methanol) Potassium bromide 0.32 g

[0276] Water is added to the whole components to adjust the whole volumeto 5,429 ml. B1 Aqueous solution of silver nitrate 2,635 ml(Concentration: 0.67 mol/L) C1 Potassium bromide 51.55 g Potassiumiodide 1.47 g

[0277] Water is added to the whole components to adjust the whole volumeto 660 ml. D1 Potassium bromide 154.9 g Potassium iodide 4.41 g Iridiumchloride (1% solution) 0.93 ml

[0278] Water is added to the whole components to adjust the whole volumeto 1,982 ml. E1 Aqueous solution of potassium Amount for bromide (0.4mol/L) controlling silver potential indicated below F1 Potassiumhydroxide 0.71 g

[0279] Water is added to adjust the whole volume to 20 ml. G1 56%Aqueous solution of acetic acid 18.0 ml H1 Anhydrous sodium carbonate1.72 g

[0280] Water is added to adjust the whole volume to 151 ml.

HO(CH₂CH₂O)_(n)—(CH(CH₃)CH₂O)₁₇—(CH₂CH₂O)mH  Compound (A)

(m+n=5 to 7)

[0281] To the solution (A1) were added one fourth of the whole quantityof the solution (B1) and the whole quantity of the solution (C1)) over 4minutes 45 seconds according to the simultaneous mixing method withusing the mixing stirrer shown in JP Sho-58-58288B and 58-58289B whilemaintaining the temperature at 45° C. and pAg at 8.09. One minute later,the whole quantity of the solution (F1) was added. In the meantime, pAgwas appropriately adjusted with the solution (E1). Six minutes later,three fourth of the whole quantity of the solution (B1) and the wholequantity of the solution (D1) were added into the foresaid solution over14 minutes 15 seconds according to the simultaneous mixing method whilemaintaining the temperature at 45° C. and pAg at 8.09. Following tostirring for 5 minutes, lowering the temperature to maintain at 40° C.,and the whole quantity of the solution (G1) was added to the solution toprecipitate silver halide emulsion. The supernatant was removed whilekeeping 2,000 ml of precipitated portion remained. Then, 10 liters ofwater was added to the precipitated portion, followed by stirring,causing precipitation of the silver halide emulsion once again. Thesupernatant was removed while keeping 1,500 ml of precipitated portionremained. Further, 10 liters of water was added to the precipitatedportion, followed by stirring, then causing precipitation of the silverhalide emulsion. The supernatant was removed while keeping 1,500 ml ofprecipitated portion remained. Then, the solution (H1) was added to theprecipitated portion, and the temperature of the solution was raised to60° C., and the solution was further stirred for 120 min. Lastly, pH ofthe solution was adjusted to 5.8, and water was added so that the weightof the silver halide emulsion comes to 1,161 g per 1 mol of silver togive photosensitive silver halide emulsion A.

[0282] This emulsion is monodispersed cube-shaped silver iodide/bromideparticles having an average particle size of 0.058 μm, a fluctuationcoefficient of the particle size of 12%, and surface [100] proportion of92%.

[0283] Next, 240 ml of a sulfur sensitizing agent S-5 in 0.5% methanolsolution and a gold sensitizing agent Au-5 in an amount equivalent toone twentieth of the amount of the sulfur sensitizing agent by mol wasadded to the emulsion, and the mixture was stirred for 120 min. at 55°C. to apply chemical sensitization.

[0284] <<Preparation of Powered Organic Silver Salt>>

[0285] Into 4,720 ml of pure water were dissolved 130.8 g of behenicacid, 67.7 g of arachidinic acid, 43.6 g of stearic acid and 2.3 g ofpalmitic acid at 80° C. Then, 540.2 ml of aqueous solution of sodiumhydroxide having a concentration of 1.5 M/L was added to the solution,followed by an addition of 6.9 ml of concentrated nitric acid. Coolingwas then applied to the solution to keep it at 55° C. so that thesolution of fatty acid sodium salt was given. While keeping thetemperature of the fatty acid sodium salt solution at 55° C., 45.3 g ofsaid photosensitive silver halide emulsion and 450 ml of pure water wereadded to the solution and stirred for 5 min.

[0286] Next, 702.6 ml of silver nitrate solution having a concentrationof 1 M/L was added over 2 min., and the solution was stirred for 10 min.to give a dispersion of an organic silver salt. Thereafter, thedispersion of organic silver salt obtained was transferred into acontainer for washing, added with deionized water, stirred, then allowedto stand to float the dispersed product of organic silver salt so as tobe separated, and the aqueous salts remained underneath was removed.Next, washing of the separated dispersed product with deionized waterwas repeated until the electric conductivity of the waste water comes toa value of 2 μS/cm, and the product was then subjected to a centrifugaldehydration to give the organic silver salt in the cake state. Thecake-like organic silver salt obtained was dried until the water contentthereof came to a rate of 0.1% under an operational condition, that isunder the atmosphere of nitrogen gas and at a temperature of blowing airat the inlet of a drier, by a air current-type drier, Flash Jet Drier(manufactured by Seishin Kigyo Co., Ltd.) to give a powered organicsilver salt A in the dried state. Note that an infrared ray moisturemeter was used for measuring the moisture content of the organic silversalt composition.

[0287] <<Preparation of Preliminary Dispersion A>>

[0288] To 1,457 g of methyl ethyl ketone was dissolved 14.57 g ofpowdered poly(vinyl butylal) (manufactured by Monsanto, Inc., ButvarB-79), followed by a gradual addition of 500 g of powdered organicsilver salt A while stirring the solution with using a dissolver,DISPERMAT, Type CA-40M (manufactured by VMA-GETZMANN, Inc.) and furtherby thorough mixing to give a preliminary dispersion A.

[0289] <<Preparation of Photosensitive Emulsion Dispersion 1>>

[0290] The preliminary dispersion A was fed to a media-type dispersingapparatus, DISPERMAT, Type: SL-C12EX (manufactured by VMA-GETZMANN,Inc.), wherein 80% of the internal space is filled with zirconia beads(manufactured by Toray Co., Ltd., Treseram) having a diameter of 0.5 mm,by using a pump so that the dispersion abides in the mill for 1.5 min.,and the dispersion was then dispersed at a mill circumferential speed of8 m/s to prepare a photosensitive emulsion dispersion 1.

[0291] <<Preparation of Stabilizing Agent Solution>>

[0292] To 4.97 g of methanol were dissolved 1.0 g of a stabilizing agent1 and 0.31 g of potassium acetate to prepare a stabilizing agentsolution.

[0293] <<Preparation of Infrared Sensitizing Colorant Solution A>>

[0294] An infrared sensitizing colorant (described in Table 1 of2.7×10⁻⁵ mol, 1.488 g of 2-chloro-benzoic acid, 2.779 g of a stabilizingagent and 365 mg of 5-methyl-2-mercaptobenzimidazole were dissolved in31.3 ml of MEK in a dark place to prepare an infrared sensitizingcolorant solution A.

[0295] <<Preparation of Additive Solution a>>

[0296] To 110 g of MEK were dissolved 27.98 g of1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane functioningas a developer, 1.54 g of 4-methylphthalic acid and 0.48 g of theforesaid dye 1 to prepare an additive solution a.

[0297] <<Preparation of Additive Solution b>>

[0298] To 40.9 g of MEK were dissolved 3.56 g of an antifoggant 2 and3.43 g of phthalazine to prepare an additive solution b.

[0299] <<Preparation of Photosensitive Layer Coating Solution>>

[0300] The foresaid photosensitive emulsion dispersion 1 (50 g) and15.11 g of MEK are kept at 21° C. while stirring under the atmosphere ofan inactive gas (nitrogen 97%), added with 390 μl of an antifoggant 1 in10% methanol solution and then further stirred for an hour, followed byan addition of calcium bromide (10% methanol solution) in a volume of494 μl and stirring for 20 min. Then, the solution was added with 167 mlof a stabilizing agent solution and allowed to stirring for 10 min.,followed by an addition of 1.32 g of the infrared sensitizing colorant Aand subsequent stirring for an hour. Temperature of the solution wasthen lowered to 13° C., followed by stirring the solution for 30 min.While keeping the temperature at 13° C., 13.31 g of poly(vinyl butylal)(manufactured by Monsanto, Inc., Butvar B-79) was added and stirred for30 min., followed by an addition of 1.084 g of tetrachlorophthalic acidin 9.4% by mass MEK solution and stirring for 5 min. While continuingthe stirring further, 12.43 g of the additive solution a, 1.6 ml of analiphatic isocyanate in 10% MEK solution manufactured by Mobay, Inc.,Desmodur N3300 and 4.27 g of the additive solution b were added to thesolution in turn, and then stirring the solution to give a desiredphotosensitive coating solution.

[0301] <<Preparation of Matting Agent Dispersion>>

[0302] Cellulose acetate butylate (manufactured by Eastman Chemical,Inc., 7.5 g of CAB171-15) was dissolved in 42.5 g of MEK. Then, to thesolution obtained was added 5 g of calcium carbonate (manufactured bySpeciality Minerals, Inc., Super-Pflex 200), and the solution wasdispersed at a revolving speed of 8,000 rpm for 30 min. by adissolver-type homogenizer to prepare a desired matting agentdispersion.

[0303] <<Preparation of Surface-protective Layer Coating Solution>>

[0304] To 865 g of MEK (methyl ethyl ketone) having been stirred wereadded 96 g of cellulose acetate butylate (manufactured by EastmanChemical, Inc., CAB 171-15), 4.5 g of polymethylmetacrylic acid(manufactured by Rohm and Haas, Inc., Pararoid A-21), 1.5 g of a vinylsulfone compound (VSC), 1.0 g of benztriazole, and 1.0 g of F-containingactive agent (manufactured by Asahi Glass Co., Ltd., Surflon KH40),dissolving them therein. Following thereto, 30 g of the foresaid mattingagent dispersion was added and stirred to prepare a desiredsurface-protective layer coating solution.

[0305] <<Coating of Photosensitive Layer Side>>

[0306] The foresaid photosensitive layer coating solution and thesurface-protective layer coating solution were simultaneously coatedonto the upper undercoat layer A-2 of the support, of which back surfacehaving been coated, in the superimposed state by an extruding(extrusion) coater to prepare the photothermographic imaging material.The coating was carried out so that the photosensitive layer was appliedwith the coating solution at a rate of 1.9 g/m² converted to the amountof silver and the surface-protective layer was formed in the thicknessafter dried of 2.5 μm. Then, the coating solutions were dried for 10min. with dried blowing air of which drying temperature being 75° C. anddew point being 10° C. to give the coating samples (photothermographicimaging materials) 1-1 through 1-14.

[0307] <<Exposure and Development Processes>>

[0308] A light exposure by the laser scanning using a light exposureapparatus that uses a semiconductor laser converted to the longitudinalmulti-mode of a wavelength of 800 to 820 nm by high-frequency folding asa light exposure source was applied from the emulsion surface side ofthe photothermographic imaging material prepared as described above. Atthis time, images were formed on the assumption that the angle betweenthe surface to be exposed of the photothermographic imaging material andthe exposing laser beams is 75°. (Note that, with this angle, it wasnoted that the degree of unevenness in the images was less comparing tothe case where the angle was set to 90°, and that images with goodquality, particularly excellent definition, were unexpectedly obtained.)

[0309] Following to the above, development process was carried out for15 seconds at 110° C. by an automatic developer including a heat drum inthe state that the protective layer of the photothermographic imagingmaterial and the surface of the heat drum are contacted with each other.At that time, the exposure and development processes were conducted in aroom maintained at a temperature of 23° C. and 50% R.H. The evaluationof the obtained images was implemented by a densitometer. The results ofthe measurement were evaluated as to the sensitivity (a reciprocal ofthe ratio of light exposure quantity giving a density that is 1.0 higherthan the non-exposed parts) and the fogging in images, expressed withthe relative values with respect to the sensitivity value of Sample 1-1being adjusted to 100, and are shown in Table 1.

[0310] “Evaluation of Shelf Life in fresh State”

[0311] Three coated samples were placed in a sealed container of whichinterior having been maintained at 25° C. and a relative humidity of 55%and kept for 7 days (forcible elapse). Among the three, the secondsample was treated in the same way as that applied for the sensitometryevaluation described above to evaluate the sensitivity and fogging.TABLE 1 AFTER PRESERVATION INFRARED AT 50° C. SAMPLE SENTISISING FOR 7DAYS No. COLORATNT FOG SENSITIVITY FOG SENSITIVITY REMARKS 1-1 2-3 0.20100 0.29 89 FOR COMPARISON 1-2 2-11 0.21 82 0.26 70 FOR COMPARISON 1-32-24 0.23 90 0.34 81 FOR COMPARISON 1-4 1-1 0.17 108 0.21 103 PRESENTINVENTION 1-5 1-4 0.16 110 0.20 105 PRESENT INVENTION 1-6 1-5 0.16 1100.20 105 PRESENT INVENTION 1-7 1-7 0.15 112 0.19 105 PRESENT INVENTION1-8 1-11 0.18 109 0.22 104 PRESENT INVENTION 1-9 1-13 0.17 108 0.21 102PRESENT INVENTION 1-10 1-16 0.15 110 0.18 105 PRESENT INVENTION 1-111-20 0.19 115 0.23 111 PRESENT INVENTION 1-12 1-23 0.15 111 0.18 108PRESENT INVENTION 1-13 1-26 0.14 110 0.16 108 PRESENT INVENTION 1-141-27 0.15 113 0.18 110 PRESENT INVENTION

[0312] As seen from Table 1, it is understood that, even though thesamples according to the present invention are provided with highphotosensitivity, they exhibit to have properties of causing lessfogging and excellent conservativeness before development processcomparing to the comparative samples.

EXAMPLE 2

[0313] Except the following reference , samples 2-1 through 2-16 of thephotothermographic imaging material were prepared according to the sameprocess described for Example 1.

[0314] <<Preparation of Infrared Sensitizing Colorant Solution B>>

[0315] Following to an addition of two kinds of infrared sensitizingcolorants those which concentration in total mol being 2.7×10⁻⁵ mol (theloading quantity of each sensitizing colorant is shown in Table 2),1.488 g of 2-chloro-benzoic acid, 2.779 g of a stabilizing agent and 365mg of 5-methyl-2-mercaptobenzimidazole were dissolved in 31.3 ml of MEKin a dark place to prepare the infrared sensitizing colorant solution B.

[0316] The light exposure, development process and various evaluationswere performed in the same way as those described in Example 1. Theresults are shown in Table 2. Note that the sensitivity of each samplewas indicated with the relative value with respect to the sensitivityvalue of the sample 2-1 being adjusted to a value of 100. TABLE 2LOADING AFTER AMOUNT(×10⁻⁵ mol) PRESERVATION AT INFRARED INFRAREDINFRARED INFRARED 50° C. SAMPLE SENSITIZING SENSITIZING SENSITIZINGSENSITIZING SENSITIV- FOR 7 DAYS No. COLORANT 1 COLORANT 2 COLORANT 1COLORANT 2 FOG ITY FOG SENSITIVITY REMARKS 2-1 2-3 — 2.7 0 0.20 100 0.2989 FOR COMPARISON 2-2 2-1 2-11 1.35 1.35 0.20 82 0.26 71 FOR COMPARISON2-3 2-1 2-12 1.62 1.08 0.24 82 0.38 71 FOR COMPARISON 2-4 2-1 — 2.7 00.18 96 0.23 89 FOR COMPARISON 2-5 2-3 2-1 1.35 1.35 0.20 97 0.28 87 FORCOMPARISON 2-6 2-5 2-24 1.35 1.35 0.21 96 0.30 88 FOR COMPARISON 2-7 1-1— 2.7 0 0.17 108 0.21 103 PRESENT INVENTION 2-8 1-1 2-1 1.35 1.35 0.15108 0.18 105 PRESENT INVENTION 2-9 1-4 2-1 1.35 1.35 0.14 111 0.16 109PRESENT INVENTION 2-10 1-4 2-1 1.08 1.62 0.13 110 0.15 105 PRESENTINVENTION 2-11 1-7 2-11 0.81 1.89 0.12 111 0.14 108 PRESENT INVENTION2-12 1-7 2-12 1.62 1.08 0.15 114 0.19 109 PRESENT INVENTION 2-13 1-162-1 1.35 1.35 0.13 110 0.15 107 PRESENT INVENTION 2-14 1-26 2-1 1.621.08 0.11 111 0.14 108 PRESENT INVENTION 2-15 1-26 2-5 1.35 1.35 0.10110 0.12 109 PRESENT INVENTION 2-16 1-27 2-1 1.35 1.35 0.12 113 0.14 112PRESENT INVENTION

[0317] As shown in Table 2, it is noted that the use of infraredsensitizing colorants according to the present invention in combinationwith other infrared sensitizing colorants allows, in spite of highphotosensitivity, to furnish with properties of less fogging andimproved conservativeness before development process comparing to thoseof the combinations of comparative examples. Further, the abovecombinations of two infrared sensitizing colorants can give equal orbetter photosensitivity, less fogging and improved conservativenessbefore development process comparing to that given by using only oneinfrared sensitizing colorant according to the present invention.

EXAMPLE 3

[0318] The photothermographic imaging material was prepared according tothe method described below. Note that “%” in the Example 3 denotes “% bymass”, unless otherwise specified.

[0319] <<Preparation of Photosensitive Silver halide Emulsion>>

[0320] (A1) Phenylcarbamoylated gelatin 88.3 g Compound A (10% methanolsolution) 10 ml Potassium bromide 0.32 g

[0321] Water was added to make the whole volume to 5429 ml.

[0322] (B1)

[0323] 0.67 mol/L Aqueous solution of Silver nitrate 2635 ml (C1)Potassium bromide 51.55 g Potassium iodide  1.47 g

[0324] Water was added to make the whole volume to 660 ml. (D1)Potassium bromide 151.6 g Potassium iodide 7.67 g Potassiumhexachloroiridate (IV) 0.93 ml Potassium hexacyanoferrate (II) 0.004 g

[0325] Water was added to make the whole volume to 1982 ml. (E1) 0.4mol/L Aqueous solution of Amount for Potassium bromide control silverpotential describe below. (F1) Potassium hydroxide 0.71 g Water wasadded to make the whole volume to 20 ml. (G1) 56% Aqueous solution ofAcetic acid 18.0 ml (H1) Anhydrous sodium carbonate 1.72 g

[0326] Water was added to make the whole volume to 151 ml.

HO(CH₂CH₂O)_(n)(CH(CH₃)CH₂O)₁₇(CH₂CH₂O)_(m)H

(m+n=5 to 7)  Compound (A)

[0327] To the solution (A1) were added one fourth of the whole volume ofthe solution (B1) and the whole volume of the solution (C1) inaccordance with the simultaneous mixing method with use of a mixingstirrer described in JP Publication Sho-58-58288 while spending 4 min.45 sec. and maintaining the temperature at 20° C. and pAg at 8.09 toform seeds. One minute later, the whole volume of the solution (F1) wasadded. During this addition, the pAg was controlled fitly with use ofthe solution (E1). Six minutes later, three fourth of the whole volumeof the solution (B1) and the whole volume of the solution (D1) wereadded in accordance with the simultaneous mixing method wile spending 14min. 15 sec. and maintaining the temperature at 20° C. and the pAg at8.09. Following to stirring of the mixture for 5 min., the temperatureof the mixture was controlled to be at 40° C., the whole volume of thesolution (G1) was added to cause silver halide emulsion to precipitate.Leaving the precipitated portion in a volume of 2000 ml, removing thesupernatant, adding 10 L of water, stirring the mixture, thereby causingthe silver halide emulsion to precipitate again. Leaving theprecipitated portion in a volume of 1500 ml, removing the supernatant,further adding 10 L of water, stirring, thereby causing the silverhalide emulsion to precipitate once more. Leaving the precipitatedportion in a volume of 1500 ml, removing the supernatant, then addingthe solution (H1), raising the temperature up to 60° C., and the mixturewas further stirred for 120 min. The pH of the emulsion was adjusted tothe final value of 5.8, water was added to the emulsion so that theemulsion has a weight of 1161 g per 1 mol of silver to give thephotosensitive silver halide emulsion A.

[0328] This emulsion contains monodispersed cubic silver bromideparticles with the average particle size of 35 nm, the variationcoefficient of the particle size of 12%, and surface [100] ratio of 92%(Content of AgI was 35 mol %).

[0329] Following to the above, this photosensitive silver halideemulsion was maintained at 60° C., the pH of which was adjusted to 6.5,added with triphenylphosphine sulfide (0.25% MEK solution) in an amountof 1.12×10⁻⁴ mol/Ag mol, followed by aging for 2 hours, and then furtheradded with 4-hydroxy-6-methyl-1,3,3a,7-tetrazaindene in an amount of1×10⁻⁵ mol/Ag mol. Then, the emulsion was quickly cooled down to 30° C.to give the photosensitive silver halide emulsion Em-1.

[0330] Besides, the photosensitive silver halide emulsion having notbeen applied with chemical sensitization is provided as Em-2.

[0331] <<Preparations of Powdered Organic Silver Salts 1 to 3>>

[0332] In 5470 ml of pure water were dissolved 52.3 g of behenic acid,27.1 g of arachidic acid, 17.45 g of stearic acid and 0.9 g of palmiticacid. Then, 270.1 ml of aqueous solution of sodium hydroxide with aconcentration of 1.5 mol/L was added while stirring at a high speed,followed by an addition of 6.9 ml of concentrated sulfuric acid, and thesolution was cooled down at 55° C. so that a solution of an organic acidsodium salt is obtained. Then, while maintaining the temperature of thesolution of organic acid sodium salt at 55° C., 380.3 ml of silvernitrate solution with a concentration of 1 mol/L was added over 2 min.Then, while stirring the solution at a high speed, a mixture of thephotosensitive silver halide emulsion Em-1 equivalent to 0.038 mol ofsilver and 450 ml of 3% gelatin solution were added over 5 min. Afterfurther stirring the solution at a high speed for 10 min., the solutionwas filtered to remove water-soluble salts. Then, washing and filtrationwith use of deionized water were repeated so that the electricconductivity of the filtrate comes to a level of 2 μm/cm, anddehydration by centrifugation was conducted, followed by continuousheating for drying until no change in the weight is recognized so thatthe powdered organic silver salt 1 is given. According to the similarprocedures, with use of the photosensitive silver halide emulsion Em-2,the powdered organic silver salt 2 was given. Besides, the powderedorganic silver salt 3 prepared without addition of the silver halide wasalso provided.

[0333] <<Preparation of Powdered Organic Silver Salt 4>>

[0334] In 4720 ml of pure water were dissolved 104.6 g of behenic acid,54.2 g of arachidic acid, 34.9 g of stearic acid and 1.8 g of palmiticacid at 80° C. Then, while stirring the solution at a high speed, 540.2ml of aqueous sodium hydroxide solution with a concentration of 1.5mol/L, and then 6.9 ml of concentrated sulfuric acid were added, and thesolution was cooled to give a solution of an organic acid sodium salt.While maintaining the temperature of the solution of an organic acidsodium salt at 55° C., the photosensitive silver halide emulsion Em-2equivalent to 0.076 mol of silver and 450 ml of pure water were added,and then stirred for 5 min. at a high speed. Then, 760.6 ml of silvernitrate solution with a concentration of 1 mol/L was added over 2 min.,then further stirred for 10 min. at a high speed, followed by filtrationfor removing water-soluble salts. Then, washing and filtration with useof deionized water were repeated so that the electric conductivity ofthe filtrate comes to a level of 2 μS/cm, performing dehydration bycentrifuge, and drying under heated nitrogen flow was carried out untilno change in the weight was recognized to thereby give the powderedorganic silver salt 4.

[0335] <<Preparation of Photosensitive Emulsion Dispersion>>

[0336] Poly(vinyl butylal) (manufactured by Monsanto Inc., Butvar B-79)in an amount of 14.57 g was dissolved in 1457 g of methyl ethyl ketone,followed by gradual addition of 500 g of the powdered organic silversalt-1 while stirring with use of a dissolver-type homogenizer, andthoroughly stirred. Then, the mixture was subjected to the dispersingprocess by a media-type dispersing apparatus (manufactured byGettzmann), 80% of which is filled with zirconium beads (manufactured byToray) with a diameter of 1 mm, at a circumferential speed of 13 m andwith a condition of continuance-in-mill time of 0.5 min. to prepare thephotosensitive emulsion dispersion-1. According to the similarprocedures, with use of the powdered organic silver salt-2, 3 and 4, thephotosensitive emulsion dispersion-2, 3 and 4 were given, respectively.

[0337] <<Preparation of Stabilizer Solution>>

[0338] A colorant stabilizer-1 in an amount of 1.0 g and 0.31 g ofpotassium acetate were dissolved in 14.35 g of methanol to prepare thestabilizer solution.

[0339] <<Preparation of Infrared-Sensitizing Colorant Solution>>

[0340] As shown in Table 3, an infrared-sensitizing colorant, 2.49 g of2-chlorobenzoic acid, 21.48 g of the colorant stabilizer-2 weredissolved in 135 g of MEK to prepare the infrared-sensitizing colorantsolution.

[0341] <<Preparation of Reducing Agent Solution>>

[0342] The reducing agent A(1,1-bis(2-hydroxy-3,5-dimethylphenyl)-3,5,5-trimethylhexane) in anamount shown in Table 3, or a compound represented by a general formula(7) in an amount equivalent to the amount shown in Table 3 was added in554 g of MEK, followed by additions of 7.39 g of 4-methylphthalic acidand 0.44 g of an infrared colorant, so that the reducing agent solutionis given.

Preparation of Coating Solution for Photosensitive Layer

[0343] The photosensitive emulsion dispersions 1, 2, 3 and 4 were mixedat the ratios shown in Table 3, respectively, and 50 g of the mixedemulsion and 15.11 g of MEK were stirred while maintaining thetemperature at 13° C., and then further added with 0.32 g of 10%methanol solution of bis(dimethylacetoamide)dibromobromate. The mixturewas then stirred for an hour. Then, 0.42 g of 10% methanol solution ofcalcium bromide, then 0.47 g of the stabilizer solution were added,followed by addition of the infrared-sensitizing colorant solution, andthe mixture was further stirred. Then, the temperature of the mixturewas lowered at 13° C., then further stirred, and added with 0.4 g of0.9% methanol solution of the colorant stabilizer solution-3. Five min.later, 15.38 g of polyvinylacetal resin (Compound P-1) was added as thebinder resin, stirred for 30 min., followed by addition of 1.1 g oftetrachlorophthalic acid (13% MEK solution) and stirred for 15 min.While further continuing stirring, 2.23 g of 22% MEK solution ofDoesmodule N3300 (manufactured by Mobay, aliphatic isocyanate), 1.8 g ofpotassium toluenethiosulfonate (1% MEK solution), 21.2 g of a reducingagent (containing the compound represented by the general formula(7)described in Table 3), 3.34 g of 12.74% MEK solution of phthalazine, and4 g of an antifogging agent were added and further stirred to give thecoating solution for the photosensitive layer.

Coating Solution for Surface Protective Layer

[0344] To 865 g of MEK having been kept stirring were added anddissolved 96 g of cellulose acetate butylate (manufactured by EastmanChemical, CAB171-15), 4.5 g of polymethylmetacrylic acid (manufacturedby Rhom & Haas, Paraloid A-21), 1.5 g of benzotriazole, 25 mg ofpotassium thiocyanate and F-containing active agent (manufactured byAsahi Glass, Surfron KH40). Then, 30 g of the matting agent solutiondescribed below was added and stirred to prepare the coating solutionfor the surface protective layer.

Preparation of Matting Agent Dispersion

[0345] Cellulose acetate butylate (manufactured by Eastman Chemical, CAB171-15) in an amount of 7.5 g was dissolved in 42.5 g of MEK, and 5 g ofcalcium carbonate (manufactured by Speciality Minerals, Super-Pflex 200)was added therein, and dispersed with use of a dissolver-typehomogenizer at 8000 rpm for 30 min. to prepare the matting agentsolution.

Preparation of Coating Solution for Back Surface

[0346] In 830 g of MEK having been kept stirring were added anddissolved 84.2 g of cellulose acetate butylate (manufactured by EastmanChemical, CAB 381-20) and 4.5 g of polyester resin (manufactured byBostic, Vitel PE2200B) . To the solution was added an infrared colorantso that the absorbance (abs) of the absorption maximum of the infraredcolorant in the coating sample for the back surface becomes 0.3, andthen, 4.5 g of a fluorine-containing active agent (manufactured by AsahiGlass, Surfron KH40) dissolved in 43.2 g of methanol and 2.3 g of afluorine-containing active agent (manufactured by Dainippon Ink,Megaface 120K) were added and thoroughly stirred until entirelydissolved. Last of all, 75 g of silica (manufactured by W. R. Grace,Siloid 64X6000) having been dispersed with use of a dissolver-typehomogenizer was added to MEK at a concentration of 1% by mass, thenstirred to prepare the coating solution for the back surface.

[0347] <<Preparation of Support>>

[0348] Corona discharge at an intensity of 0.2 kV·A·min/m² was appliedto the both sides of a polyethylene terephthalate film base (thickness,175 μm) colored in blue with a density of 0.170. On the one side, anundercoating layer a was coated with use of the coating solution A forthe undercoating layer described below so that the undercoating layer ais formed with a dried thickness of 0.2 μm. Further, on the other side,an undercoating layer b was coated with use of the coating solution Bfor the undercoating layer described below so that the undercoatinglayer b is formed with a thickness of 0.1 μm. Then, the undercoatinglayers were treated with heat at 130° C. for 15 min. in a heat-applyingtype oven including a film feeding apparatus comprising a plurality ofrollers.

[0349] (Coating solution A for Undercoating Layer)

[0350] Copolymer latex (solid content 30%) of butyl acrylate/t-butylacrylate/styrene/2-hydroxyethyl acrylate (ratio, 30/20/25/25%) in anamount of 270 g, 0.6 g of a surface-active agent (UL-1) and 0.5 g ofmethyl cellulose were mixed. Further, 1.3 g of silica particles(manufactured by Fuji Silicia, Siloid 350) was added into 100 g ofwater, and the mixture was subjected to dispersing process with use of asupersonic dispersing apparatus (manufactured by ALEX Corporation:Ultrasonic Generator, Frequency, 25 kHz, 600W) for 30 min. Last of all,the dispersion was then added with water to make the whole volume to1000 ml so that the coating solution A for the undercoating layer isprepared.

[0351] (Coating Solution B for Undercoating Layer)

[0352] The colloidal tin oxide dispersion in an amount of 37.5 g, 3.7 gof copolymer latex liquid (solid content 30%) of butyl acrylate/t-butylacrylate/styrene/2-hydroxyethyl acrylate (ratio, 20/30/25/25%), 14.8 gof copolymer latex liquid (solid content 30%) of butylacrylate/styrene/glycidyl metacrylate (ratio, 40/20/40%), and 0.1 g ofsurface-active agent (UL-1) were mixed , and water was added to themixture to make the whole volume to 1000 ml so that the coating solutionB for the undercoating layer is prepared.

[0353] (Colloidal Tin Oxide Dispersion)

[0354] Stannic chloride hydrate in an amount of 65 g was dissolved in2000 ml of water/ethanol-mixed solution to prepare a uniformly-mixedsolution. Then, the solution was boiled to give a coprecipitatedproduct. Silver nitrate was fed by dropping into distillated waterhaving been used for washing the precipitate to check no presence of thereaction of chlorine ions, then, adding distillated water to the washedprecipitate to make the whole volume to 2000 ml. Furthermore, 40 ml of30% aqueous ammonia solution was added, and heating was applied to theaqueous solution to condense the solution until the volume is reduced toa volume of 470 ml so that the colloidal tin oxide dispersion isprepared.

[0355] <<Preparation of Photothermographic Imaging Material>>

[0356] The combinations of the emulsion dispersions as shown in Table 3were respectively applied to the both sides of the support having beenprovided with undercoating to form the photosensitive layer and the backlayer, and the support was then dried to prepare the photothermographicimaging material.

[0357] (Coating to Photosensitive Layer Side)

[0358] The coating solution for the photosensitive layer and the coatingsolution for the protective layer both prepared as described above wererespectively applied in the manner of simultaneous superimposition ontothe support in this order from the support side by an extruding coaterto form the photosensitive layer and the surface protective layer sothat the photothermographic imaging material (Sample No. 1 through 20)was prepared. Note that the coated amount of silver was 1.5 g/m², thedrying was performed at 75° C. for 5 min. using dry wind of which dewpoint temperature is 10° C. The surface protective layer was formed witha dried thickness of 1.5 μm.

[0359] (Coating to Back Surface Side)

[0360] The coating solution for the back surface prepared as describedabove was applied by an extruding coater so that the layer is formedwith a dried thickness of 3 μm, and then dried. The temperature appliedfor the drying was 100° C., and drying was performed for 5 min. usingdried wind of which dew point temperature is 10° C.

[0361] The detailed compositions of the photothermographic imagingmaterials (Sample Nos. 1 through 20) prepared as described above arepresented in Table 3. TABLE 3 INFRA- RED SENSI- LOAD- SAM- TIZINGINFRARED INGS PLE COLOR- LOADINGS SENSITIZING LOADINGS REDUCING mol/ No.EMULSION DISPERSION ANT mol/Agmol COLORANT mol/Agmol AGENT Agmol REMARKS1 DISPERSION 2:DISPERSION 3 = 1:1 DYE-A 6.64 × 10⁻⁵ — — REDUCING 0.365FOR AGENT A COMPARISON 2 DISPERSION 2:DISPERSION 3 = 1:1 DYE-A 3.32 ×10⁻⁵ DYE-C 3.32 × 10⁻⁵ REDUCING 0.365 FOR AGENT A COMPARISON 3DISPERSION 2:DISPERSION 3 = 1:1 DYE-B 3.32 × 10⁻⁵ DYE-A 3.32 × 10⁻⁵REDUCING 0.365 FOR AGENT A COMPARISON 4 DISPERSION 2:DISPERSION 3 = 1:111-5 6.64 × 10⁻⁵ — — REDUCING 0.365 FOR AGENT A REFERENCE 5 DISPERSION2:DISPERSION 3 = 1:1 — — 12-13 6.64 × 10⁻⁵ REDUCING 0.365 PRESENT AGENTA INVENTION 6 DISPERSION 2:DISPERSION 3 = 1:1 11-6 1.80 × 10⁻⁵ 12-114.20 × 10⁻⁵ REDUCING 0.365 FOR AGENT A REFERENCE 7 DISPERSION2:DISPERSION 3 = 1:1 11-11 1.20 × 10⁻⁵ 12-10 4.80 × 10⁻⁵ REDUCING 0.365PRESENT AGENT A INVENTION 8 DISPERSION 2:DISPERSION 3 = 1:1 11-4 2.00 ×10⁻⁵ 12-10 2.00 × 10⁻⁵ REDUCING 0.365 PRESENT 11-12 2.00 × 10⁻⁵ AGENT AINVENTION 9 DISPERSION 3:DISPERSION 1 = 1:1 11-4 3.00 × 10⁻⁵ 12-10 1.70× 10⁻⁵ REDUCING 0.365 PRESENT 12-20 1.70 × 10⁻⁵ AGENT A INVENTION 10DISPERSION 2:DISPERSION 3 = 1:1 11-4 0.60 × 10⁻⁵ 12-10 3.36 × 10⁻⁵REDUCING 0.365 PRESENT 11-11 0.60 × 10⁻⁵ 12-13 1.44 × 10⁻⁵ AGENT AINVENTION 11 DISPERSION 2:DISPERSION 3 = 1:1 11-4 3.32 × 10⁻⁵ 12-10 3.32× 10⁻⁵ 3-70 0.091 PRESENT REDUCING 0.274 INVENTION AGENT A 12 DISPERSION3:DISPERSION 1 = 1:1 11-4 3.32 × 10⁻⁵ 12-10 3.32 × 10⁻⁵ 3-12 0.243PRESENT REDUCING 0.122 INVENTION AGENT A 13 DISPERSION 3:DISPERSION 1 =1:1 11-4 3.32 × 10⁻⁵ 12-10 3.32 × 10⁻⁵ 3-72 0.182 PRESENT 3-7 0.182INVENTION 14 DISPERSION 2:DISPERSION 3 = 1:1 11-4 3.32 × 10⁻⁵ 12-10 3.32× 10⁻⁵ 3-7 0.365 PRESENT INVENTION 15 DISPERSION 3:DISPERSION 1 = 1:111-4 3.32 × 10⁻⁵ 12-10 3.32 × 10⁻⁵ 3-23 0.365 PRESENT INVENTION 16DISPERSION 3:DISPERSION 1 = 1:1 11-4 3.32 × 10⁻⁵ 12-10 3.32 × 10⁻⁵ 3-380.347 PRESENT INVENTION 17 DISPERSION 3:DISPERSION 1 = 1:1 11-4 3.32 ×10⁻⁵ 12-10 3.32 × 10⁻⁵ 3-34 0.347 PRESENT INVENTION 18 DISPERSION3:DISPERSION 1 = 1:1 11-4 3.32 × 10⁻⁵ 12-10 3.32 × 10⁻⁵ 3-72 0.347PRESENT INVENTION 19 DISPERSION 4 11-4 3.32 × 10⁻⁵ 12-10 3.32 × 10⁻⁵3-71 0.347 PRESENT INVENTION 20 DISPERSION 4 11-4 3.32 × 10⁻⁵ 12-10 3.32× 10⁻⁵ 3-15 0.347 PRESENT INVENTION

[0362]

[0363] <<Evaluation of Photothermographic Imaging Materials 1>>

[0364] The characteristics of the photothermographic imaging materials(Sample Nos. 1 to 20) prepared as described above were evaluated inaccordance with the following procedures.

[0365] (Measurements of Dmin, Dmax and Sensitivity)

[0366] Each sample was converted to a half size sheet and then subjectedto the image-like exposure with use of semiconductor laser of 810 nm.Note that the exposure operation was carried out by setting the anglebetween the exposure surface of the sample and the exposing laser beamsat 80 degree, and the power output of the laser at 57.45 mm/sec, 30 mW,and the high-frequency superimposition was outputted in the verticalmulti-mode. The thermal development processing was carried out at 125°C. for 13.5 sec. with use of a heating drum to apply heat evenly.Densities of the thermally-developed images of the respective samplesobtained as described above were measured by an optical densitometer(manufactured by Konica, PD-82), and a characteristic curve based on thedensity D and the quantity of exposure Log(1/E) was prepared, with whichthe minimum density (Dmin=Fog density), the sensitivity, the color tone_(Y) and the maximum density (Dmax) were measured. Note that thesensitivity was defined as the inverse logarithm of the quantity ofexposure that gives a density of 1.0 higher than the minimum density.The gamma in the photographic characteristic values represents the slope(color tone Y) of the characteristic curve. Namely, the gamma denotesthe slope between the point of (minimum density+0.25) to the point of(minimum density+2.5). Note that results of the Dmin, D max and thesensitivity are represented with the relative values to the convertedvalue of the sample 1 of 100.

[0367] (Evaluation on Shelf Stability (Shelf Stability in Fresh State))

[0368] The prepared samples were placed in a sealed container, theinside of which having been maintained at 25° C., 55% RH and in oxygenatmosphere (101 kPa), and stored for a period of 7 days at 55° C.,respectively. These samples were provided for the forcibly-deterioratedsamples, respectively. For the comparison, the same samples were storedin a shaded container, the inside of which having been maintained at 25°C. and 55% RH, for a period of 7 days, and those samples were providedfor the sample for check. The exposure and heat development processingswere applied to each of the samples obtained as described above inaccording to the same procedures as described above. The minimum density(fog density) was measured for each sample according to the same methodsas described above, and the increase of the fog (ΔDmin1) was worked outbased on the following equation, which was used as a scale for the shelfstability (shelf stability in fresh state) and represented with therelative value to the converted value of the sample 1 of 100.

ΔDmin1=(Fog Density of Forcibly-deteriorated Sample)−(Fog Density ofCheck Sample)

[0369] (Evaluation on Resistance of Image Against Light)

[0370] The samples thermally developed as described were respectivelyplaced in a room maintained at 25° C. and 55% RH for a period of 7 daysunder a fluorescent light. Then, the optical density in the minimumdensity portion (the portion of Dmin) before and after the foresaidplacement was measured for the respective samples. From the measureddensity, the variation (ΔDmin2) of the minimum density (Dmin) wasdetermined in accordance with the following equation. The given valueswere used as the scale of the shelf stability, which was expressed withthe relative values to the converted value of the sample 1 of 100.

ΔDmin2=(Dmin after exposure to fluorescent light)−(Dmin before exposureto fluorescent light)

[0371] Note that the temperature on the used light source table was 45°C., and the brightness was 8000 Lux. The results are represented withthe relative values to the converted value of the sample 1 of 100.

[0372] (Evaluation on Resistance against Development ProcessingEnvironment: Process Environment ΔSensitivity)

[0373] In the thermal development processing, a dry laser imager was setin a temperature/humidity-controlled room, and exposures and thermaldevelopment were applied to the photographic materials under fourdifferent conditions, that is, at 32° C. and 70% RH, at 32° C. and 10%RH, at 13° C. and 70% RH, and at 13° C. and 25% RH. The evaluations forthe given images were conducted in accordance with the photographicperformance evaluations as described above. The differences between themaximum value and the minimum value in the sensitivity under therespective four conditions were compared. The lesser values arepreferred.

[0374] The results obtained from the above evaluations were shown inTable 4. TABLE 4 PROCESS LIGHT SHELF LIFE IN SAMPLE ENVIRONMENTDURABILITY FRESH STATE No. D min SENSITIVITY D max ΔSENSITIVITY ΔD min2ΔD min2 REMARKS 1 100 100 100 100 100 100 FOR COMPARISON 2 99 100 98 102103 104 FOR COMPARISON 3 101 99 98 101 101 102 FOR COMPARISON 4 92 101101 95 93 89 PRESENT INVENTION 5 93 105 103 91 89 90 PRESENT INVENTION 689 114 109 80 81 85 PRESENT INVENTION 7 85 119 110 78 82 84 PRESENTINVENTION 8 84 118 109 81 80 85 PRESENT INVENTION 9 82 116 108 79 83 80PRESENT INVENTION 10 86 120 110 82 84 83 PRESENT INVENTION 11 85 118 11483 79 80 PRESENT INVENTION 12 84 120 118 78 74 76 PRESENT INVENTION 1378 124 123 71 68 65 PRESENT INVENTION 14 76 121 120 73 67 64 PRESENTINVENTION 15 75 120 120 74 67 65 PRESENT INVENTION 16 70 117 118 72 6863 PRESENT INVENTION 17 73 118 119 73 70 66 PRESENT INVENTION 18 74 118120 74 69 67 PRESENT INVENTION 19 84 111 110 80 84 81 PRESENT INVENTION20 80 108 109 78 81 83 PRESENT INVENTION

[0375] It is noted from Table 4 shown above that the respective samplesaccording to this invention produce less fogs, being highly-sensitive,giving sufficient highest density, and being excellent in theirresistance against light and in the shelf stability. In addition to theabove, it was found that the color tone Y of the respective samplesaccording to this invention was in a range of 2.5 to 5.0, exhibitingtheir suitability to be used for the photosensitive materials formedical use.

[0376] <<Evaluation on Photothermographic Imaging Material 2>>

[0377] Evaluations on silver color tone were conducted for thephotothermographic imaging materials (samples 1, 8, 12, 13 and 19)prepared as described above in accordance with the following procedures.

[0378] (Evaluation on Silver Color Tone)

[0379] Exposure processing was applied to the respective samples underthe condition of giving the optical density as Dmin of 0.5, 1.0 and 1.5in accordance with the same procedures as described above. Then, thesample was developed to prepare the wedge sample formed in four stairsincluding the unexposed portions. From the respective wedge densityportions prepared as described above, u* and v* were calculated byCM-3600d (manufactured by Minolta co., Ltd.) in accordance with themeasuring method for u*, V* and a*, b* in the space of CIE 1976 colors.On a graph, wherein the transverse axis represents u* or a* (green tored colors) and the vertical axis represents v* or b* (blue to yellowcolors), u* and v* measured on the low density (optical density 0.2) tothe high density (optical density 1.5) of Dmin were plotted, and thelinear regression line was determined to work out the R square values,the intersect, the angle, and the slope.

[0380] It is noted from the characteristic values determined by thelinear regression, the preferred color tone with which no fatigue ineyes during diagnosis is caused is moderate yellow. Concretely, themeasured characteristic values as described above preferably accord tothe following criterion.

[0381] Angle and Slope: The angle closer to 45 degree, or the slope (tanθ) closer to 1.0 represents better color balance in the range of the lowdensity portion to the high density portion.

[0382] Intersect: The range of +3 to −3 is preferred, and the range of+2 to −2 is more preferred.

[0383] R square value: The value closer to 1.0 represents less variationand less dispersion in colors in the range of the low density portion tothe high density portion, more reliability, and more accuracy.

[0384] Furthermore, visual evaluations were conducted for the preparedsilver images, and the quality of silver color tone was determined inaccordance with the following criterion.

[0385] A: Optimally suitable silver color tone at visual diagnosis.

[0386] B: Acceptable silver color tone at visual diagnosis.

[0387] D: Silver color tone with which eyes get tired and diagnosis ismade hard.

[0388] The results obtained in the evaluations described above are shownin Table 5. TABLE 5 SAMPLE SILVER SQUARED No. INCLINATION COLOR TONEANGLE INTERCEPT VALUE REMARKS 1 D 0.08 4.31° −8.70 0.07 FOR COMPARISON 8B 0.39 21.29° −6.32 0.79 PRESENT INVENTION 12 A 0.89 41.55° −2.14 0.93PRESENT INVENTION 13 A 1.09 47.48° 0.20 1.00 PRESENT INVENTION 19 B 0.4323.17° −6.86 0.83 PRESENT INVENTION

[0389] It is apparently noted from Table 5 that the ective samplescomposed according to this invention superior in the characteristics interms of the maticity diagram and in the silver color tone based hevisual observation.

[0390] The entire disclosure of JP Tokugan-2003-079517 d on Mar. 24,2003 including specification, claims, ings and summary and JPTokugan-2003-102726 filed on Apr. 7, 2003 including specification,claims, drawings and summary is incorporated herein by reference in itsentirety.

What is claimed is:
 1. A photothermographic imaging material comprisingphotosensitive silver halide on at least one side of a support, and atleast one of compounds represented by the following general formula (1);

wherein the L₁ ₁to the L₁₇ represent each independently a hydrogen atom,a halogen atom, an amino group, an alkylthio group, an arylthio group, alower alkyl group, a lower alkoxy group, an aryloxy group, an aryl groupor a heterocyclic group, or a non-metal atom group required for bondingthe L₁₁ and the L₁₂, the L₁₂ and the L₁₃, the L₁₃ and the L₁₄, the L₁₅and the L₁₆, and the L₁₆ and the L₁₇, respectively, to form 5- to7-membered rings; the R₁ and the R₂ represent each independently analiphatic group; the R₁ and the L₁₁, and the R₂ and the L₁₄ can bebonded each other to form a 5- to 7-membered cyclic structurerespectively; the Ar₁ and the Ar₂ represent each independently an arylgroup or a heterocyclic group; the X₁₁ represents an ion required foroffsetting electric charges in a molecules; and n represents the numberof ions required for offsetting electric charges in the molecules. 2.The material of claim 1, comprising at least one of compoundsrepresented by the following general formula (2);

wherein the L₂₁ to the L₂₄ represent each independently a hydrogen atom,a halogen atom, an amino group, an alkylthio group, an arylthio group, alower alkyl group, a lower alkoxyl group, an aryloxy group, an aryl, aheterocyclic group, or a non-metal atom group required for bonding theL₂₁ and the L₂₂, the L₂₂ and the L₂₃, and the L₂₃ and the L₂₄ can bebonded each other respectively to form 5- to 7-membered rings; the R₃and the R₄ represent each independently an aliphatic group; the R₃ andthe L₂₁, and the R₄ and the L₂₄ can be bonded each other to form a 5- to7-membered cyclic structure, respectively; the X₂₁ represents an ionrequired for offsetting electric charges in the molecules; the mrepresents the number of ions required for offsetting electric chargesin the molecules; the R₂₁ to the R₂₄ represent each independently ahydrogen atom, an alkyl group or an aryl group; and the R₂₅ to the R₃₂represent a group capable of being substituted on a benzene ring; theR₂₅ and the R₂₆, the R₂₆ and the R₂₇, the R₂₇ and the R₂₈, the R₂₉ andthe R₃₀, the R₃₀ and the R₃₁ and the R₃₁ and the R₃₂ can be bonded eachother respectively to form cyclic structures; the R₂₇ is neither an arylgroup nor a heterocyclic group.
 3. The material of claim 1, wherein thecompound represented by the general formula (1) is a compoundrepresented by the following general formula (3);

wherein the L₁₁ to the L₁₇ in the general formula (3) are synonymouswith the L₁₁ to the L₁₇ in the general formula (1); the R₁ and the R₂ inthe general formula (3) are synonymous with the R₁ and the R₂ in thegeneral formula (1); the X₁₁ in the general formula (3) is synonymouswith the X₁₁ in the general formula (1); the n in the general formula(3) is synonymous with the n in the general formula (1); and the Ar₃ andthe Ar₄ represent each independently an aryl group.
 4. The material ofclaim 1, wherein the compound represented by the general formula (1) isa compound represented by the following general formula (4);

wherein the L₁₁ to the L₁₇ in the general formula (4) are synonymouswith the L₁₁ to the L₁₇ in the general formula (1); the R₁ and the R₂ inthe general formula (4) are synonymous with the R₁ and the R₂ in thegeneral formula (1); the X₁₁ in the general formula (4) is synonymouswith the X₁₁ in the general formula (1); the n in the general formula(4) is synonymous with the n in the general formula (1).
 5. The materialof claim 1, wherein the compound represented by the general formula (1)is a compound represented by the following general formula (5);

wherein the L₁₁ to the L₁₄ in the general formula (5) are synonymouswith the L₁₁ to the L₁₄ in the general formula (1); the R₁ and the R₂ inthe general formula (5) are synonymous with the R₁ and the R₂ in thegeneral formula (1); the X₁₁ in the general formula (5) is synonymouswith the X₁₁ in the general formula (1); the n in the general formula(5) is synonymous with the n in the general formula (1); and the R₃₁ tothe R₃₄ represent each independently a hydrogen atom, an alkyl group oran aryl group.
 6. The material of claim 2, wherein the compoundrepresented by the general formula (2) is a compound represented by thefollowing general formula (6);

wherein the L₂₁ to the L₂₄ in the general formula (6) are synonymouswith the L₂₁ to the L₂₄ in the general formula (2); the R₃ and the R₄ inthe general formula (6) are synonymous with the R₃ and the R₄ in thegeneral formula (2); the X₂₁ in the general formula (6) is synonymouswith the X₂₁ in the general formula (2); and the m in the generalformula (6) is synonymous with the m in the general formula (2); the R₂₁to the R₂₄ in the general formula (6) are synonymous with the R₂₁ to theR₂₄ in the general formula (2); and the R₄₁ and the R₄₂ represent eachindependently an unsubstituted lower alkyl group, a cycloalkyl group, anaralkyl group, an aryl group or a heterocyclic group.
 7. The material ofclaim 1, comprising a compound represented by the following generalformula (7);

wherein the R₁₁ and the R₁₂ represent each independently hydrogen atom,3- to 10-membered nonaromatic cyclic group or 5- or 6-memberd aromaticcyclic group; the R₁₃ and the R₁₄ represent each independently hydrogenatom, alkyl group; aryl group or a heterocyclic group, the Q representsa substituent on the benzene ring; n is 0 or an integer of 1 or 2; andthe Q are same or different from one another when the Q is plural. 8.The material of claim 1, wherein the photosensitive silver halide ischemically sensitized.
 9. The material of claim 1, comprising aphotosensitive emulsion comprising the photosensitive silver halide anda non-photosensitive aliphatic silver carboxylate; wherein thephotosensitive silver halide is not contained in a synthesis of thenon-photosensitive aliphatic silver halide, and is mixed with thenon-photosensitive aliphatic silver carboxylate after a completion ofthe synthesis to prepare the photosensitive emulsion.